a(n) = 3^n*(2*n)!/(n!)^2.

A098658

a(n) = 3^n*(2*n)!/(n!)^2.

Terms

    a(0) =1a(1) =6a(2) =54a(3) =540a(4) =5670a(5) =61236a(6) =673596a(7) =7505784a(8) =84440070a(9) =956987460a(10) =10909657044a(11) =124965162504

External references