A032309 "EFK" (unordered, size, unlabeled) transform of 2,4,6,8,...

1, 2, 4, 14, 20, 50, 112, 190, 328, 666, 1340, 2038, 3740, 5954, 10792, 19542, 30048, 48290, 80164, 124694, 204484, 347610, 515184, 810750, 1240296, 1932722, 2887820, 4557838, 7126652, 10463330, 15768168, 23499934

Offset

0,2

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..5000

C. G. Bower, Transforms (2)

Formula

G.f.: Product_{k >= 1} (1 + 2*k*x^k).

Mathematica

nmax=40; CoefficientList[Series[Product[(1+2*k*x^k), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Dec 19 2015 *)

Prog

(PARI) seq(n)={Vec(prod(k=1, n, 1 + 2*k*x^k + O(x*x^n)))} \\ Andrew Howroyd, Sep 20 2018

Crossrefs

Cf. A022629, A032302, A265951, A265955.

Sequence in context: A342605 A032398 A245764 * A008519 A243934 A071865

Adjacent sequences: A032306 A032307 A032308 * A032310 A032311 A032312

Keyword

nonn

Author

Christian G. Bower

Extensions

a(0)=1 prepended by Andrew Howroyd, Sep 20 2018

Status

approved