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%I #5 Sep 10 2017 14:53:24
%S 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 281,67,334,80,379,29,436,481,191,121,277,142,631,154,277,175,781,67,
%U 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 Compound filter: a(n) = P(A003557(n), A000010(n)), where P(n,k) is sequence A000027 used as a pairing function.
%H Antti Karttunen, <a href="/A291756/b291756.txt">Table of n, a(n) for n = 1..16385</a>
%F a(n) = (1/2)*(2 + ((A003557(n)+A000010(n))^2) - A003557(n) - 3*A000010(n)).
%o (PARI)
%o A000010(n) = eulerphi(n);
%o A003557(n) = n/factorback(factor(n)[, 1]); \\ This function from _Charles R Greathouse IV_, Nov 17 2014
%o A291756(n) = (1/2)*(2 + ((A003557(n)+A000010(n))^2) - A003557(n) - 3*A000010(n));
%Y Cf. A000010, A000027, A003557, A291757, A291764.
%K nonn
%O 1,3
%A _Antti Karttunen_, Sep 10 2017
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