A333956 G.f. A(x) satisfies: A(x) = x - Sum_{k>=2} sigma(k) * A(x)^k.

1, -3, 14, -82, 546, -3932, 29816, -234438, 1893469, -15612527, 130870098, -1111844944, 9552257052, -82846987926, 724385135208, -6378457007916, 56511184375548, -503399149941744, 4505973904735072, -40508206566645846, 365585085331313000, -3311041732282565260

Offset

1,2

Comments

Reversion of the sum of divisors function (A000203).

Links

Table of n, a(n) for n=1..22.

Index entries for reversions of series

Mathematica

nmax = 22; CoefficientList[InverseSeries[Series[Sum[x^k/(1 - x^k)^2, {k, 1, nmax}], {x, 0, nmax}], x], x] // Rest

Crossrefs

Cf. A000203, A050389, A333957.

Sequence in context: A032080 A367078 A291535 * A194091 A186737 A367972

Adjacent sequences: A333953 A333954 A333955 * A333957 A333958 A333959

Keyword

sign

Author

Ilya Gutkovskiy, Apr 22 2020

Status

approved