G.f. A(x) satisfies: A(x) = (1/(1 - x)) * A(x^2)^2*A(x^3)^3*A(x^4)^4* ... *A(x^k)^k* ...

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =17a(5) =28a(6) =72a(7) =122a(8) =282a(9) =493a(10) =1027a(11) =1790a(12) =3673a(13) =6300a(14) =12205a(15) =21117a(16) =39782a(17) =67989a(18) =124937a(19) =212189a(20) =381705a(21) =644625a(22) =1136315a(23) =1905352a(24) =3312916a(25) =5513005a(26) =9443362a(27) =15624026a(28) =26445046a(29) =43451200