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A216669 Total number of parts in all partitions of n into 2 sizes of parts (A002133). 2
2, 5, 14, 20, 39, 52, 74, 102, 134, 158, 208, 259, 284, 361, 409, 488, 538, 634, 678, 838, 857, 1006, 1038, 1270, 1264, 1495, 1500, 1776, 1761, 2084, 2062, 2443, 2300, 2795, 2680, 3194, 3076, 3544, 3403, 4080, 3804, 4518, 4282, 5037, 4673, 5626, 5127, 6088 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

COMMENTS

Also column k=2 of A255768. - Omar E. Pol, Jul 26 2015

LINKS

Alois P. Heinz, Table of n, a(n) for n = 3..1000

FORMULA

a(n) = Sum_{k=2..n-1} k * A216665(n,k).

MATHEMATICA

nn=40; ss=Sum[Sum[y^2 x^(i+j)/(1-y x^i)/(1-y x^j), {j, 1, i-1}], {i, 1, nn}]; CoefficientList[Series[D[ss, y]/.y->1, {x, 0, nn}], x]

CROSSREFS

Cf. A002133, A216665, A255768.

Sequence in context: A089410 A118670 A228958 * A015633 A176191 A265248

Adjacent sequences:  A216666 A216667 A216668 * A216670 A216671 A216672

KEYWORD

nonn

AUTHOR

Geoffrey Critzer, Sep 13 2012

STATUS

approved

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Last modified July 9 18:08 EDT 2020. Contains 335545 sequences. (Running on oeis4.)