Some definitions of interest.
coprime	Def CoPrime(a,b) == GCD(a;b;1)
	Thm* a,b:. CoPrime(a,b)  Prop
fib	Def fib(n) == if n=0  n=1 1 else fib(n-1)+fib(n-2) fi  (recursive)
	Thm* n:. fib(n)
not	Def A == A  False
	Thm* A:Prop. (A)  Prop

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