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A032309 "EFK" (unordered, size, unlabeled) transform of 2,4,6,8,... 3
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 (list; graph; refs; listen; history; text; internal format)
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: A295401 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

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Last modified October 17 07:57 EDT 2018. Contains 316276 sequences. (Running on oeis4.)