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Question 21427: Parity Subsequences Need a Strict All-Later Epsilon Witness

On this page
  1. Original question and givens
  2. Definition and scope
  3. Step-by-step derivation
  4. Reverse checks
  5. Result
  6. This question review and source binding

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R0041-21427 · q-20261014-advance-20261109-r02-bolzano-weierstrass-theorem-real-0052

Original question and givens

Use a_n=L+(−1)^n*c/(n+shift) for every n≥0, L=2/3, c=2>0, shift=3≥1, parity=1 and epsilon=1/11>0. The infinite index rule is k(j)=2j+parity for every j≥0. Give (parity, index_rule, limit, epsilon, J, value_at_k_J, strict_tail_certificate, certificate).

  • G001 — Use a_n=L+(−1)^n*c/(n+shift) for every n≥0, L=2/3, c=2>0, shift=3≥1, parity=1 and epsilon=1/11>0. The infinite index rule is k(j)=2j+parity for every j≥0. Give (parity, index_rule, limit, epsilon, J, value_at_k_J, strict_tail_certificate, certificate).

Definition and scope

Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate.

Step-by-step derivation

S001 · implies

Before

source operation=bw-oscillatory-tail;original snapshot and mathematics retained

After

explicit ordered source output fields=[parity, index_rule, limit, epsilon, J, value_at_k_J, strict_tail_certificate, certificate]

Conditions: none

Retain the historical interface marker while listing ordered output fields without JavaScript.Fields and tags are not extra mathematical evidence;fixed No markers retain their claim scope.

Step identifiers and dependencies

Rule: source_ordered_interface_explicit_without_javascript · Uses: G001

S002 · implies

Before

ORIGINAL a_n=2/3+(-1)^n*(2)/(n+3) for EVERY n>=0;parity=1

After

k(j)=2j+1 for ALL j>=0;k(j+1)-k(j)=2>0;selected sign=-1;whole sequence bounded by |L|+c/shift

Conditions: none

The parity rule is an infinite strictly increasing index map.Selected signs are fixed and errors equal c/(2j+parity+shift).The whole sequence is bounded;its monotonicity is not a premise for this subsequence certificate.

Step identifiers and dependencies

Rule: bw_parity_whole_law_and_infinite_strict_index · Uses: G001, S001

S003 · calculation

Before

bw c over epsilon := div(2, 1/11)

After

bw c over epsilon = 22

Conditions: none

Substitute the original roles and established intermediates exactly,retaining order,signs and quantified conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

bw index multiple := mul(2, 10)

After

bw index multiple = 20

Conditions: none

Substitute the original roles and established intermediates exactly,retaining order,signs and quantified conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

bw actual source index := sum(1, 20)

After

bw actual source index = 21

Conditions: none

Substitute the original roles and established intermediates exactly,retaining order,signs and quantified conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · calculation

Before

bw witness denominator := sum(21, 3)

After

bw witness denominator = 24

Conditions: none

Substitute the original roles and established intermediates exactly,retaining order,signs and quantified conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S005

S007 · calculation

Before

bw witness distance := div(2, 24)

After

bw witness distance = 1/12

Conditions: none

Substitute the original roles and established intermediates exactly,retaining order,signs and quantified conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S006

S008 · calculation

Before

bw predecessor distance := div(2, 22)

After

bw predecessor distance = 1/11

Conditions: none

Substitute the original roles and established intermediates exactly,retaining order,signs and quantified conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S007

S009 · implies

Before

bw:c=2,shift=3,epsilon=1/11;index(q)=2q+1;c/epsilon=22;floor=22

After

least nonnegative witness=10;actual source index=21;distance=1/12<epsilon;predecessor distance=1/11;no predecessor evaluated when witness0

Conditions: none

Strict distance<epsilon means the denominator exceeds c/epsilon,so its integer threshold is floor(c/epsilon)+1.Round the affine index upward and clamp only the witness to0.Check the predecessor only when positive;equality still fails.

Step identifiers and dependencies

Rule: tail_strict_least_index_not_equality_or_negative_predecessor · Uses: G001, S008

S010 · implies

Before

bw:positive c=2,epsilon=1/11,shift=3,stride=2,offset=1;least witness=10

After

for EVERY integer q>=10,denominator=2q+1+3>=witness denominator>0,so 0<distance<=(1/12)<epsilon

Conditions: none

This is an algebraic inequality for every later index,not convergence guessed from one evaluated term.Positive increasing denominators and a fixed positive numerator control the whole tail;the predecessor check proves minimality only.

Step identifiers and dependencies

Rule: tail_all_later_quantified_from_positive_denominator_growth · Uses: G001, S009

S011 · calculation

Before

bw at selected k(J) denominator := sum(21, 3)

After

bw at selected k(J) denominator = 24

Conditions: none

Substitute the original roles and established intermediates exactly,retaining order,signs and quantified conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S010

S012 · calculation

Before

bw at selected k(J) unsigned tail := div(2, 24)

After

bw at selected k(J) unsigned tail = 1/12

Conditions: none

Substitute the original roles and established intermediates exactly,retaining order,signs and quantified conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S011

S013 · calculation

Before

bw at selected k(J) signed value := sub(2/3, 1/12)

After

bw at selected k(J) signed value = 7/12

Conditions: none

Substitute the original roles and established intermediates exactly,retaining order,signs and quantified conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S012

Reverse checks

  • S013 · premise_and_result_audit — Recompute bw at selected k(J) signed value with exact rational arithmetic, not rounded decimals.
  • S012 · premise_and_result_audit — Recompute bw at selected k(J) unsigned tail with exact rational arithmetic, not rounded decimals.
  • S011 · premise_and_result_audit — Recompute bw at selected k(J) denominator with exact rational arithmetic, not rounded decimals.
  • S010 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S009 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S008 · premise_and_result_audit — Recompute bw predecessor distance with exact rational arithmetic, not rounded decimals.
  • S007 · premise_and_result_audit — Recompute bw witness distance with exact rational arithmetic, not rounded decimals.
  • S006 · premise_and_result_audit — Recompute bw witness denominator with exact rational arithmetic, not rounded decimals.
  • S005 · premise_and_result_audit — Recompute bw actual source index with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute bw index multiple with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute bw c over epsilon with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

(1, k(j)=2j+1, 2/3, 1/11, 10, 7/12, Yes, forall_j_ge_J_symbolic_subsequence_tail)

The full substitutions and premise checks give the original answer; source identity,format and status are unchanged.

This question review and source binding

Review date: 2026-10-26

Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.

Source hashes and review receipts
  • input commit: 0f7be61e2c22317a4075561dc822c87d881a50db
  • original question SHA-256: de1f130871404832454e8492e73723200f7b053567454bcad741aa380cc965d0
  • candidate record SHA-256: c638f02467cdcd45d500569ba0dda7245fdea1d97a52bea4aa36f1fe703219d2
  • semantic review receipt SHA-256: 8f134403487694af4c70d2e00ec84bab542043ef4b3c54517c04f3c409c0262a
  • question-first witness SHA-256: ad772845088ed8e99f87f90d4264b05ea97be35775305a02011af5ee35f0f4ce
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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