G.f.: Sum_{n>=0} (n+x)^n * x^n / (1 + n*x + x^2)^n.
A187742
G.f.: Sum_{n>=0} (n+x)^n * x^n / (1 + n*x + x^2)^n.
Terms
- a(0) =1a(1) =1a(2) =4a(3) =14a(4) =66a(5) =384a(6) =2640a(7) =20880a(8) =186480a(9) =1854720a(10) =20321280a(11) =243129600a(12) =3153427200a(13) =44068147200a(14) =660064204800
External references
- oeis: A187742