a(n) = binomial(8*n+2,n)/(4*n+1).

Terms

a(0) =1a(1) =2a(2) =17a(3) =200a(4) =2728a(5) =40508a(6) =635628a(7) =10368072a(8) =174047640a(9) =2987139122a(10) =52177566870a(11) =924548764752