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A321949 Column k=4 of triangle A257673.

%I A321949 #10 Jan 30 2021 22:50:17
%S A321949 1,12,78,376,1509,5340,17234,51796,147054,398388,1037560,2612520,
%T A321949 6387965,15221412,35446980,80865304,181076216,398660292,864186408,
%U A321949 1846759404,3894731430,8113669352,16710519860,34049851236,68687627812,137257430140,271842916654
%N A321949 Column k=4 of triangle A257673.
%H A321949 Alois P. Heinz, <a href="/A321949/b321949.txt">Table of n, a(n) for n = 4..5000</a>
%F A321949 G.f.: (-1 + Product_{k>=1} 1 / (1 - x^k)^k)^4. - _Ilya Gutkovskiy_, Jan 30 2021
%p A321949 b:= proc(n, k) option remember; `if`(n=0, 1, k*add(
%p A321949       b(n-j, k)*numtheory[sigma][2](j), j=1..n)/n)
%p A321949     end:
%p A321949 a:= n-> (k-> add(b(n, k-i)*(-1)^i*binomial(k, i), i=0..k))(4):
%p A321949 seq(a(n), n=4..35);
%Y A321949 Column k=4 of A257673.
%K A321949 nonn
%O A321949 4,2
%A A321949 _Alois P. Heinz_, Nov 22 2018