cp's OEIS Frontend

A341031 Numbers k such that A066840(k) is a square.

%I A341031 #11 Feb 03 2021 11:11:34
%S A341031 1,2,3,4,6,8,10,14,16,17,22,26,32,34,38,46,54,58,62,64,74,82,86,94,
%T A341031 106,118,122,128,134,142,146,158,166,171,178,194,202,206,214,218,226,
%U A341031 254,255,256,262,274,278,298,302,314,326,334,346,358,362,382,386,394,398,422,446,451,454,458,466
%N A341031 Numbers k such that A066840(k) is a square.
%H A341031 Robert Israel, <a href="/A341031/b341031.txt">Table of n, a(n) for n = 1..2500</a>
%e A341031 a(6) = 8 is a term because A066840(8) = 4 = 2^2.
%p A341031 N:= 1000: # for terms <= N
%p A341031 G:= add(numtheory:-mobius(n)*n*x^(2*n)/((1-x^n)*(1-x^(2*n))^2), n=1..N/2):
%p A341031 S:= series(G, x, N+1):
%p A341031 A66840:= [seq(coeff(S, x, j), j=1..N)]:
%p A341031 select(t -> issqr(A66840[t]), [$1..N]);
%Y A341031 Includes A000079 and A100484.
%Y A341031 Cf. A066840.
%K A341031 nonn
%O A341031 1,2
%A A341031 _J. M. Bergot_ and _Robert Israel_, Feb 02 2021