

A116684


Sum of the even parts in all partitions of n into distinct parts.


3



0, 0, 2, 2, 4, 6, 14, 18, 22, 34, 50, 66, 88, 118, 154, 202, 248, 320, 412, 512, 636, 794, 972, 1194, 1454, 1766, 2134, 2576, 3092, 3696, 4426, 5254, 6214, 7364, 8672, 10196, 11986, 14014, 16360, 19084, 22190, 25746, 29860, 34516, 39846, 45952, 52848
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OFFSET

0,3


COMMENTS



LINKS



FORMULA

G.f.=2*product(1+x^j,j=1..infinity)*sum((jx^(2j)/(1+x^(2j)), j=1..infinity)).


EXAMPLE

a(9)=34 because in the partitions of 9 into distinct parts, namely, [9],[81],[72],[6,3],[6,2,1],[5,4],[5,3,1] and [4,3,2], the sum of the even parts is 8+2+6+6+2+4+4+2=34.


MAPLE

f:=2*product(1+x^j, j=1..60)*sum((j*x^(2*j)/(1+x^(2*j)), j=1..35)): fser:=series(f, x=0, 55): seq(coeff(fser, x, n), n=0..50);


MATHEMATICA

Map[Total[Select[Flatten[d[#]], EvenQ]] &, 1 + Range[30]] )
(* Peter J. C. Moses, Mar 14 2014 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



