a(n) = binomial(2^n + n - 1, n).A060690a(n) = binomial(2^n + n - 1, n).Terms a(0) =1a(1) =2a(2) =10a(3) =120a(4) =3876a(5) =376992a(6) =119877472a(7) =131254487936External referencesoeis: A060690