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

1, 2, 3, 4, 6, 8, 10, 14, 16, 17, 22, 26, 32, 34, 38, 46, 54, 58, 62, 64, 74, 82, 86, 94, 106, 118, 122, 128, 134, 142, 146, 158, 166, 171, 178, 194, 202, 206, 214, 218, 226, 254, 255, 256, 262, 274, 278, 298, 302, 314, 326, 334, 346, 358, 362, 382, 386, 394, 398, 422, 446, 451, 454, 458, 466

Offset: 1

Author

J. M. Bergot and Robert Israel, Feb 02 2021

Keywords

• nonn

Examples

			a(6) = 8 is a term because A066840(8) = 4 = 2^2.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..2500

Crossrefs

Includes A000079 and A100484.

Cf. A066840.

Programs

Maple

N:= 1000: # for terms <= N
G:= add(numtheory:-mobius(n)*n*x^(2*n)/((1-x^n)*(1-x^(2*n))^2), n=1..N/2):
S:= series(G, x, N+1):
A66840:= [seq(coeff(S, x, j), j=1..N)]:
select(t -> issqr(A66840[t]), [$1..N]);