G.f.: Sum_{n>=0} Product_{k=1..n} (1 - 1/(1+k*x)^3).

A222033

G.f.: Sum_{n>=0} Product_{k=1..n} (1 - 1/(1+k*x)^3).

Terms

    a(0) =1a(1) =3a(2) =12a(3) =64a(4) =429a(5) =3459a(6) =32578a(7) =350928a(8) =4254819a(9) =57339343a(10) =850210608a(11) =13755324192a(12) =241123857361

External references