proposition: Lemma FR_fib_sum11 i: FR ((fib i.+4) * 4) = ((i./2)*3).+1.
proof: Proof. by rewrite fib_times4 (FR_fib_sum2) // - add2n - (add2n i.+2) !addnK. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path fintype div bigop binomial) mathcomp(prime finset ssralg ssrnum ssrint)