G.f.: Sum_{n>=0} x^n * Product_{k=1..n} (1 + k*x) / (1 - x - k*x^2).
A231291
G.f.: Sum_{n>=0} x^n * Product_{k=1..n} (1 + k*x) / (1 - x - k*x^2).
Terms
- a(0) =1a(1) =1a(2) =3a(3) =9a(4) =29a(5) =99a(6) =355a(7) =1333a(8) =5213a(9) =21163a(10) =88899a(11) =385413a(12) =1720637a(13) =7894827a(14) =37166563a(15) =179254501a(16) =884548253a(17) =4460597131a(18) =22962705027a(19) =120557527941a(20) =644952640253
External references
- oeis: A231291