a(n) = Sum_{k=0..n} binomial(3*n+2,4*k).

Terms

a(0) =1a(1) =6a(2) =72a(3) =496a(4) =4096a(5) =32896a(6) =261632a(7) =2098176a(8) =16777216a(9) =134209536a(10) =1073774592a(11) =8589869056a(12) =68719476736a(13) =549756338176