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A281590
Indices k such that A284896(k-1) and A284896(k) have a different sign.
3
1, 4, 9, 15, 20, 27, 33, 41, 48, 56, 64, 72, 80, 89, 98, 107, 116, 126, 136, 146, 156, 166, 176, 187, 198, 208, 219, 231, 242, 253, 265, 276, 288, 300, 312, 324, 337, 349, 362, 374, 387, 400, 413, 426, 439, 452, 465, 479, 492, 506, 519, 533, 547, 561, 575
OFFSET
1,2
LINKS
EXAMPLE
A284896(8) = 73, A284896(9) = -45, sign is changed, so 9 is in the sequence.
A284896(14) = -66, A284896(15) = 2794, sign is changed, so 15 is in the sequence.
MATHEMATICA
nmax = 1000; A284896 = Rest[CoefficientList[Series[Product[1/(1 + x^k)^(k^2), {k, 1, nmax}], {x, 0, nmax}], x]]; csign = {1}; Do[If[(A284896[[n]] < 0 && A284896[[n+1]] >= 0) || (A284896[[n]] >= 0 && A284896[[n+1]] < 0), csign = Flatten[{csign, n + 1}]], {n, 1, Length[A284896] - 1}]; csign
CROSSREFS
Sequence in context: A189459 A313272 A301680 * A112781 A166131 A313273
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Apr 14 2017
STATUS
approved