a(n) = binomial(4*n, 2*n)*(2*n)!/(2^n*n!).

A359761

a(n) = binomial(4*n, 2*n)*(2*n)!/(2^n*n!).

Terms

    a(0) =1a(1) =6a(2) =210a(3) =13860a(4) =1351350a(5) =174594420a(6) =28109701620

External references