a(n) = binomial(2^n + n, n).A132683a(n) = binomial(2^n + n, n).Terms a(0) =1a(1) =3a(2) =15a(3) =165a(4) =4845a(5) =435897a(6) =131115985a(7) =138432467745External referencesoeis: A132683