3911846400domain: NAppears in sequencesa(n) = Product_{k=1..n} binomial(2*k,k).at n=6A007685Consider Pascal's triangle A007318; a(n) = product of terms at +45 degrees slope with the horizontal.at n=13A073617Number of up-down runs in all permutations of {1,2,...,n}.at n=12A186371