proposition: Lemma fib_times_c_is_fib4 n k : fib n == 3 * (fib k) = ((k==0) && (n==0)) || (((k==1) || (k==2)) &&(n==4)).
proof: Proof. rewrite (lucas_times_fib_is_fib k n 2) /= (eq_sym 2 k). by case kz: (k==2); rewrite ? orbF //= (eqP kz) orbb. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path fintype div bigop binomial) mathcomp(prime finset ssralg ssrnum ssrint)