cp's OEIS Frontend

A291756 Compound filter: a(n) = P(A003557(n), A000010(n)), where P(n,k) is sequence A000027 used as a pairing function.

%I A291756 #5 Sep 10 2017 14:53:24
%S A291756 1,1,2,5,7,2,16,25,31,7,46,12,67,16,29,113,121,31,154,38,67,46,232,59,
%T A291756 281,67,334,80,379,29,436,481,191,121,277,142,631,154,277,175,781,67,
%U A291756 862,212,328,232,1036,261,1135,281,497,302,1327,334,781,355,631,379,1654,138,1771,436,706,1985,1129,191,2146,530,947,277,2416,607,2557,631,951,668,1771
%N A291756 Compound filter: a(n) = P(A003557(n), A000010(n)), where P(n,k) is sequence A000027 used as a pairing function.
%H A291756 Antti Karttunen, <a href="/A291756/b291756.txt">Table of n, a(n) for n = 1..16385</a>
%F A291756 a(n) = (1/2)*(2 + ((A003557(n)+A000010(n))^2) - A003557(n) - 3*A000010(n)).
%o A291756 (PARI)
%o A291756 A000010(n) = eulerphi(n);
%o A291756 A003557(n) = n/factorback(factor(n)[, 1]); \\ This function from _Charles R Greathouse IV_, Nov 17 2014
%o A291756 A291756(n) = (1/2)*(2 + ((A003557(n)+A000010(n))^2) - A003557(n) - 3*A000010(n));
%Y A291756 Cf. A000010, A000027, A003557, A291757, A291764.
%K A291756 nonn
%O A291756 1,3
%A A291756 _Antti Karttunen_, Sep 10 2017