%I #9 Mar 11 2020 09:48:17
%S 0,0,1,1,0,0,2,2,2,2,0,0,3,3,3,6,3,3,3,0,4,4,4,8,8,8,8,8,4,4,9,5,5,10,
%T 10,15,15,15,15,15,15,10,16,11,11,17,12,18,24,24,24,30,30,30,30,24,31,
%U 31,25,26,26,27,34,41,35,42,49,49,56,56,56,56,64
%N G.f.: Sum_{k>=1} (k * x^(k*(k+1)) * Product_{j=1..k} (1 + x^j)).
%H Vaclav Kotesovec, <a href="/A333181/b333181.txt">Table of n, a(n) for n = 0..10000</a>
%F a(n) ~ c * A333198^sqrt(n), where c = 0.2895947615240435716456...
%F Limit_{n->infinity} A333180(n) / a(n) = A060006 = (1/2 + sqrt(23/3)/6)^(1/3) + (1/2 - sqrt(23/3)/6)^(1/3) = 1.32471795724474602596090885...
%t nmax = 100; CoefficientList[Series[Sum[n*x^(n*(n+1))*Product[1+x^k, {k, 1, n}], {n, 0, Sqrt[nmax]}], {x, 0, nmax}], x]
%t nmax = 100; p = 1; s = 0; Do[p = Expand[p*(1 + x^k)*x^(2*k)]; p = Take[p, Min[nmax + 1, Exponent[p, x] + 1, Length[p]]]; s += k*p;, {k, 1, Sqrt[nmax]}]; Take[CoefficientList[s, x], nmax + 1]
%Y Cf. A333153, A333179, A333180.
%K nonn
%O 0,7
%A _Vaclav Kotesovec_, Mar 10 2020