A373032 - OEIS

A373032

Expansion of Sum_{k>=1} (-1)^(k+1) * k^2 * x^(k*(k+1)) / (1 - x^k).

0, 1, 1, 1, 1, -3, 1, -3, 1, -3, 1, 6, 1, -3, 10, -3, 1, 6, 1, -19, 10, -3, 1, -10, 1, -3, 10, -19, 1, 31, 1, -19, 10, -3, 26, -10, 1, -3, 10, 6, 1, -30, 1, -19, 35, -3, 1, -46, 1, 22, 10, -19, 1, -30, 26, 30, 10, -3, 1, -21, 1, -3, 59, -19, 26, -30, 1, -19, 10, 71

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OFFSET

1,6

LINKS

Table of n, a(n) for n=1..70.

FORMULA

a(n) = Sum_{d|n, d < sqrt(n)} (-1)^(d+1) * d^2.

MATHEMATICA

nmax = 70; CoefficientList[Series[Sum[(-1)^(k + 1) k^2 x^(k (k + 1))/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest

CROSSREFS

Cf. A056924, A064027, A070039, A321543, A333809, A333810, A339353, A344300, A372625, A373031.

Sequence in context: A050345 A348611 A070039 * A227991 A319137 A074122

Adjacent sequences: A373029 A373030 A373031 * A373033 A373034 A373035

KEYWORD

sign

AUTHOR

Ilya Gutkovskiy, May 20 2024

STATUS

approved