fact: Definition card_wbase2' k n := #|[set t :k.-tuple 'I_3 | wbase2 t == n ]|.
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)