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
Keywords
Links
- Vaclav Kotesovec, Table of n, a(n) for n = 0..5000
- C. G. Bower, Transforms (2)
Programs
-
Mathematica
nmax=40; CoefficientList[Series[Product[(1+2*k*x^k), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Dec 19 2015 *) -
PARI
seq(n)={Vec(prod(k=1, n, 1 + 2*k*x^k + O(x*x^n)))} \\ Andrew Howroyd, Sep 20 2018
Formula
G.f.: Product_{k >= 1} (1 + 2*k*x^k).
Extensions
a(0)=1 prepended by Andrew Howroyd, Sep 20 2018