6854491840domain: NAppears in sequencesS(n,n) + S(n-1,n-2) + S(n-2,n-4) + ... + S(n-k+1,n-2k+2), where k = [ (n+1)/2 ] and S(i,j) are Stirling numbers of second kind.at n=23A024428Expansion of Sum_{n>=0} x^n / Product_{k=1..2*n} (1 - k*x).at n=12A229286