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Number of partitions of n into parts of 21 kinds.
2

%I #29 Jun 17 2018 09:09:51

%S 1,21,252,2233,16170,100926,560945,2837418,13266099,57994475,

%T 239170239,937026279,3507380170,12601619226,43628951025,146036139347,

%U 473924014599,1494785958435,4591920193357,13764656869425,40328218603134

%N Number of partitions of n into parts of 21 kinds.

%C a(n) is the Euler transform of A010860. - _Alois P. Heinz_, Oct 17 2008

%H Seiichi Manyama, <a href="/A023019/b023019.txt">Table of n, a(n) for n = 0..1000</a>

%H N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>

%H <a href="/index/Pro#1mxtok">Index entries for expansions of Product_{k >= 1} (1-x^k)^m</a>

%F a(0) = 1, a(n) = (21/n)*Sum_{k=1..n} A000203(k)*a(n-k) for n > 0. - _Seiichi Manyama_, Mar 27 2017

%p with (numtheory): a:= proc(n) option remember; `if`(n=0, 1, add (add (d*21, d=divisors(j)) *a(n-j), j=1..n)/n) end: seq (a(n), n=0..40); # _Alois P. Heinz_, Oct 17 2008

%t CoefficientList[Series[1/QPochhammer[x]^21, {x, 0, 30}], x] (* _Indranil Ghosh_, Mar 27 2017 *)

%o (PARI) Vec(1/eta(x)^21 + O(x^30)) \\ _Indranil Ghosh_, Mar 27 2017

%Y Cf. 21st column of A144064. - _Alois P. Heinz_, Oct 17 2008

%K nonn

%O 0,2

%A _David W. Wilson_, Jun 14 1998