G.f. satisfies: A(x) = Sum_{n>=0} x^n * Product_{k=1..n} (A(x) - x^k).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =7a(5) =21a(6) =60a(7) =181a(8) =557a(9) =1741a(10) =5531a(11) =17778a(12) =57741a(13) =189191a(14) =624634a(15) =2076037a(16) =6940372a(17) =23322865a(18) =78739090a(19) =266933783a(20) =908335157a(21) =3101467309a(22) =10622722567a(23) =36486959455a(24) =125652837052a(25) =433761554314