A306706 - OEIS

%I #5 Mar 05 2019 18:18:27

%S 1,1,-1,2,-2,0,1,2,-4,-3,7,4,-4,-14,6,10,12,-14,0,-26,3,7,60,11,-27,

%T -99,-26,6,126,94,58,-87,-180,-201,-46,145,282,330,142,-21,-515,-573,

%U -716,-15,423,1519,1128,1197,-783,-1378,-3264,-1892,-1574,2155,2679,6075,3376,3243

%N Expansion of Sum_{k>=0} x^(k*(k+1)/2) / Product_{j=1..k} (1 + x^j)^j.

%t nmax = 57; CoefficientList[Series[Sum[x^(k (k + 1)/2)/Product[(1 + x^j)^j, {j, 1, k}], {k, 0, nmax}], {x, 0, nmax}], x]

%Y Cf. A003406, A206138.

%K sign

%O 0,4

%A _Ilya Gutkovskiy_, Mar 05 2019