Exponential generating function is exp(2*x/(1-x))/(1-x).

A087912

Exponential generating function is exp(2*x/(1-x))/(1-x).

Terms

    a(0) =1a(1) =3a(2) =14a(3) =86a(4) =648a(5) =5752a(6) =58576a(7) =671568a(8) =8546432a(9) =119401856a(10) =1815177984a(11) =29808908032a(12) =525586164736

External references