cp's OEIS Frontend

A286467 Compound filter (prime signature of n & prime signature of the n-th Fibonacci number): a(n) = P(A101296(n), A286545(n)), where P(n,k) is sequence A000027 used as a pairing function.

%I A286467 #14 Aug 05 2017 16:16:23
%S A286467 1,3,5,9,5,19,5,33,18,25,5,51,5,25,40,73,5,72,12,84,40,25,5,128,69,25,
%T A286467 71,84,5,180,12,146,40,25,40,242,23,40,40,198,12,180,5,177,177,40,5,
%U A286467 337,31,216,40,84,12,284,59,308,140,40,12,478,12,40,177,339,40,180,23,177,140,387,12,610,12,59,216,177,59,309,12,540,332,40,5,608,59,40,59
%N A286467 Compound filter (prime signature of n & prime signature of the n-th Fibonacci number): a(n) = P(A101296(n), A286545(n)), where P(n,k) is sequence A000027 used as a pairing function.
%C A286467 Nonsquare semiprimes pq for which F(pq) is also a semiprime is given by the positions where 25's occur in this sequence: 10, 14, 22, 26, 34, 94, (any more terms?). This is a subsequence of A072381.
%H A286467 Antti Karttunen, <a href="/A286467/b286467.txt">Table of n, a(n) for n = 1..1300</a> (based also on the b-file of A278245 provided by Hans Havermann)
%F A286467 a(n) = (1/2)*(2 + ((A101296(n) + A286545(n))^2) - A101296(n) - 3*A286545(n)).
%o A286467 (Scheme) (define (A286467 n) (* (/ 1 2) (+ (expt (+ (A101296 n) (A286545 n)) 2) (- (A101296 n)) (- (* 3 (A286545 n))) 2)))
%Y A286467 Cf. A000027, A046523, A072381, A101296, A278245, A286545.
%Y A286467 Cf. A083668 (positions of 5's).
%K A286467 nonn
%O A286467 1,2
%A A286467 _Antti Karttunen_, May 17 2017