cp's OEIS Frontend

A286560 Compound filter (summands of A004001 & summands of A005185): a(n) = P(A286541(n), A286559(n)), where P(n,k) is sequence A000027 used as a pairing function, with a(1) = a(2) = 0.

%I A286560 #9 Feb 16 2025 08:33:45
%S A286560 0,0,1,2,5,41,71,71,198,313,484,922,1153,1201,2105,1565,2588,4046,
%T A286560 5001,7443,7443,8851,10671,19589,16570,16935,22254,25313,25313,25313,
%U A286560 42891,28793,32768,52795,65504,59178,73355,89033,88632,107660,129045,129045,153471,167646,167646,182446,182446,336130,197244,233297,330472,307358,270167,355325,378466,332156
%N A286560 Compound filter (summands of A004001 & summands of A005185): a(n) = P(A286541(n), A286559(n)), where P(n,k) is sequence A000027 used as a pairing function, with a(1) = a(2) = 0.
%H A286560 Antti Karttunen, <a href="/A286560/b286560.txt">Table of n, a(n) for n = 1..10000</a>
%H A286560 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PairingFunction.html">Pairing Function</a>
%F A286560 a(1) = a(2) = 0, for n > 2, a(n) = (1/2)*(2 + ((A286541(n)+A286559(n))^2) - A286541(n) - 3*A286559(n)).
%o A286560 (Scheme) (define (A286560 n) (if (<= n 2) 0 (* (/ 1 2) (+ (expt (+ (A286541 n) (A286559 n)) 2) (- (A286541 n)) (- (* 3 (A286559 n))) 2))))
%Y A286560 Cf. A004001, A005185, A284019, A286541, A286559, A286569.
%K A286560 nonn
%O A286560 1,4
%A A286560 _Antti Karttunen_, May 18 2017