Main derivation
S01 · implies
Before
p\text{ prime},\quad1\le a<pAfter
\gcd(a,p)=1\Rightarrow\exists a^{-1}\pmod pConditions: none
Rule: calc · Uses: G1
Leaf basis: calc
A prime has only proper positive divisor 1, so every nonzero class is coprime and Bezout provides an inverse.
S02 · implies
Before
a=a^{-1}\pmod pAfter
a^2\equiv1\Rightarrow p\mid(a-1)(a+1)\Rightarrow a\equiv1\text{ or }-1\pmod pConditions: none
Rule: calc · Uses: G1, S01
Leaf basis: calc
Euclid's lemma determines all self-inverse classes; for p>2,1 and -1 are distinct.
S03 · implies
Before
p>2,\quad a\ne a^{-1}After
\{a,a^{-1}\}\text{ disjoint inverse pairs},\quad aa^{-1}\equiv1\pmod pConditions: none
Rule: calc · Uses: G1, S01, S02
Leaf basis: calc
Inversion is an involution, partitioning all non-self-inverse classes into disjoint two-element pairs.
S04 · implies
Before
\prod_{a=1}^{p-1}a\text{ paired as above}After
(p-1)!\equiv1\cdot(-1)\cdot1\equiv-1\pmod p
Conditions: none
Rule: calc · Uses: G1, S02, S03
Leaf basis: calc
In the product of all nonzero classes, ordinary inverse pairs give 1 and self-inverses 1,-1 leave -1.
S05 · implies
Before
p=2
After
(2-1)!=1\equiv-1\pmod2
Conditions: none
Rule: calc · Uses: G1, S01
Leaf basis: calc
At even prime 2,1 and -1 are the same single class; the formula holds directly.
S06 · implies
Before
p=7,\quad a=1,2,3,4,5,6
After
a^{-1}=1,4,5,2,3,6\text{ respectively}Conditions: none
Rule: calc · Uses: G1, S01, S02
Leaf basis: calc
The complete six-entry inverse list gives pairs {1},{6},{2,4},{3,5}.
S07 · implies
Before
j=1,2,3,4,5,6
After
j!\bmod7=1,2,6,3,1,6\text{ respectively};\quad6!=720\equiv6\pmod7Conditions: none
Rule: calc · Uses: G1, S04, S06
Leaf basis: calc
A complete incremental factorial table independently checks prime 7, with residue 6 representing -1.
S08 · implies
Before
n>1\text{ composite},\quad1<d<n,\quad d\mid nAfter
d\mid(n-1)!
Conditions: none
Rule: calc · Uses: G1
Leaf basis: calc
A composite has a proper divisor d, which appears as a factor in 1 through n-1, so d divides the factorial.
S09 · implies
Before
(n-1)!\equiv-1\pmod n,\quad d\mid n,\quad d\mid(n-1)!
After
d\mid((n-1)!+1)\text{ and }d\mid(n-1)!\Rightarrow d\mid1\text{ impossible}Conditions: none
Rule: calc · Uses: G1, S08
Leaf basis: calc
If a composite passed Wilson, subtraction would make d>1 divide 1, a contradiction, proving the converse.
S10 · implies
Before
n>1,\quad\text{prime direction and composite contradiction}After
n\text{ prime}\iff(n-1)!\equiv-1\pmod nConditions: none
Rule: mko_definition · Uses: G1, S04, S05, S07, S09
Leaf basis: mko_definition
Both directions together with p=2 complete the equivalence; the modulo-7 table is only an instance certificate.