Nuprl Lemma : primrec-induction-factorial
∀n:ℕ. (∃x:ℤ [((n)! = x ∈ ℤ)])
Proof
Definitions occuring in Statement : 
fact: (n)!
, 
nat: ℕ
, 
all: ∀x:A. B[x]
, 
sq_exists: ∃x:A [B[x]]
, 
int: ℤ
, 
equal: s = t ∈ T
Definitions unfolded in proof : 
uall: ∀[x:A]. B[x]
, 
so_lambda: λ2x.t[x]
, 
member: t ∈ T
, 
subtype_rel: A ⊆r B
, 
nat_plus: ℕ+
, 
so_apply: x[s]
, 
implies: P 
⇒ Q
, 
all: ∀x:A. B[x]
, 
prop: ℙ
, 
sq_exists: ∃x:A [B[x]]
, 
has-value: (a)↓
, 
uimplies: b supposing a
, 
nat: ℕ
, 
not: ¬A
, 
ge: i ≥ j 
, 
satisfiable_int_formula: satisfiable_int_formula(fmla)
, 
exists: ∃x:A. B[x]
, 
false: False
, 
top: Top
, 
and: P ∧ Q
, 
squash: ↓T
, 
true: True
, 
guard: {T}
, 
iff: P 
⇐⇒ Q
, 
rev_implies: P 
⇐ Q
, 
decidable: Dec(P)
, 
or: P ∨ Q
Lemmas referenced : 
primrec-induction, 
sq_exists_wf, 
equal-wf-T-base, 
fact_wf, 
nat_plus_wf, 
int_subtype_base, 
nat_wf, 
fact0_redex_lemma, 
equal-wf-base, 
value-type-has-value, 
int-value-type, 
fact_unroll_1, 
nat_properties, 
satisfiable-full-omega-tt, 
intformand_wf, 
intformeq_wf, 
itermAdd_wf, 
itermVar_wf, 
itermConstant_wf, 
intformle_wf, 
int_formula_prop_and_lemma, 
int_formula_prop_eq_lemma, 
int_term_value_add_lemma, 
int_term_value_var_lemma, 
int_term_value_constant_lemma, 
int_formula_prop_le_lemma, 
int_formula_prop_wf, 
add-subtract-cancel, 
equal_wf, 
squash_wf, 
true_wf, 
iff_weakening_equal, 
decidable__le, 
intformnot_wf, 
int_formula_prop_not_lemma, 
le_wf
Rules used in proof : 
cut, 
introduction, 
extract_by_obid, 
sqequalHypSubstitution, 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
isectElimination, 
thin, 
sqequalRule, 
lambdaEquality, 
intEquality, 
hypothesisEquality, 
hypothesis, 
applyEquality, 
setElimination, 
rename, 
independent_functionElimination, 
lambdaFormation, 
because_Cache, 
dependent_set_memberFormation, 
natural_numberEquality, 
baseClosed, 
callbyvalueReduce, 
independent_isectElimination, 
addEquality, 
multiplyEquality, 
dependent_pairFormation, 
int_eqEquality, 
dependent_functionElimination, 
isect_memberEquality, 
voidElimination, 
voidEquality, 
independent_pairFormation, 
computeAll, 
imageElimination, 
equalityTransitivity, 
equalitySymmetry, 
universeEquality, 
imageMemberEquality, 
productElimination, 
dependent_set_memberEquality, 
unionElimination
Latex:
\mforall{}n:\mBbbN{}.  (\mexists{}x:\mBbbZ{}  [((n)!  =  x)])
Date html generated:
2018_05_21-PM-06_59_42
Last ObjectModification:
2017_07_26-PM-05_02_10
Theory : general
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