a(n) = Sum_{k=0..n} binomial(4*n+k-1,n-k).

Terms

a(0) =1a(1) =4a(2) =30a(3) =245a(4) =2080a(5) =18058a(6) =159081a(7) =1415955a(8) =12700610a(9) =114602665a(10) =1039058616a(11) =9457679477a(12) =86366895485a(13) =790883332085