a(n) = Sum_{k=0..n} 3^(n-k)*C(2*n,n-k).

A386826

a(n) = Sum_{k=0..n} 3^(n-k)*C(2*n,n-k).

Terms

    a(0) =1a(1) =7a(2) =67a(3) =694a(4) =7459a(5) =81922a(6) =912718a(7) =10273228a(8) =116522275a(9) =1329569290a(10) =15244087642a(11) =175472098996

External references