G.f.: A(x) = exp( Sum_{n>=1} sigma(n^2)*x^n/n ), a power series in x with integer coefficients.

Terms

a(0) =1a(1) =1a(2) =4a(3) =8a(4) =20a(5) =38a(6) =88a(7) =162a(8) =336a(9) =624a(10) =1211a(11) =2195a(12) =4109a(13) =7295a(14) =13190a(15) =23072a(16) =40618a(17) =69838a(18) =120486a(19) =204006a(20) =345595a(21) =577387a(22) =962961a(23) =1588483a(24) =2613930a(25) =4262138a(26) =6928799a(27) =11179251a(28) =17976330a(29) =28720552