a(n) = Sum_{k=0..n-1} binomial(3*k+1,k) * binomial(3*n-3*k,n-k-1).
A386617
a(n) = Sum_{k=0..n-1} binomial(3*k+1,k) * binomial(3*n-3*k,n-k-1).
Terms
- a(0) =0a(1) =1a(2) =10a(3) =81a(4) =610a(5) =4436a(6) =31626a(7) =222681a(8) =1554772a(9) =10790721a(10) =74560728a(11) =513452604a(12) =3526463304a(13) =24168921568a(14) =165357919850
External references
- oeis: A386617