G.f.: Sum_{n>=0} x^n * Product_{k=1..n} (1 + n*k*x) / (1 + x + n*k*x^2).
A208236
G.f.: Sum_{n>=0} x^n * Product_{k=1..n} (1 + n*k*x) / (1 + x + n*k*x^2).
Terms
- a(0) =1a(1) =1a(2) =1a(3) =4a(4) =10a(5) =50a(6) =208a(7) =1290a(8) =7456a(9) =55982a(10) =411796a(11) =3650514a(12) =32484460a(13) =332970374a(14) =3468625588a(15) =40420787250a(16) =481757564956
External references
- oeis: A208236