Expansion of Sum_{k>=0} (x * (1 + (k * x)^2))^k.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =9a(5) =28a(6) =81a(7) =369a(8) =1753a(9) =7323a(10) =36337a(11) =207401a(12) =1114345a(13) =6308368a(14) =40326033a(15) =256982157a(16) =1658573497a(17) =11650405774a(18) =83966740913a(19) =608348063576