%I #10 Jan 30 2021 22:50:17

%S 1,12,78,376,1509,5340,17234,51796,147054,398388,1037560,2612520,

%T 6387965,15221412,35446980,80865304,181076216,398660292,864186408,

%U 1846759404,3894731430,8113669352,16710519860,34049851236,68687627812,137257430140,271842916654

%N Column k=4 of triangle A257673.

%H Alois P. Heinz, <a href="/A321949/b321949.txt">Table of n, a(n) for n = 4..5000</a>

%F G.f.: (-1 + Product_{k>=1} 1 / (1 - x^k)^k)^4. - _Ilya Gutkovskiy_, Jan 30 2021

%p b:= proc(n, k) option remember; `if`(n=0, 1, k*add(

%p b(n-j, k)*numtheory[sigma][2](j), j=1..n)/n)

%p end:

%p a:= n-> (k-> add(b(n, k-i)*(-1)^i*binomial(k, i), i=0..k))(4):

%p seq(a(n), n=4..35);

%Y Column k=4 of A257673.

%K nonn

%O 4,2

%A _Alois P. Heinz_, Nov 22 2018