fact: Fixpoint fuscP2 p := match p with | xO n => let: (a,b) := fuscP2 n in (a, a+b) | xI n => let: (a,b) := fuscP2 n in (a+b,b) | xH => (1,1) end.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq choice fintype order bigop ssralg) mathcomp(div ssrnum ssrint rat prime path binomial) mathcomp(tuple finset) gaia(fibm)