G.f.: A(x) = Sum_{n>=0} x^n/(1-x)^(n^2).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =83a(6) =363a(7) =1730a(8) =8889a(9) =48829a(10) =284858a(11) =1755325a(12) =11374092a(13) =77208275a(14) =547261631a(15) =4039201624a(16) =30967330941a(17) =246084049137