569768domain: NAppears in sequencesG.f.: A(x) = Sum_{n>=0} x^n / Product_{k=1..n} (1-x^k)^(n-k+1).at n=17A206119Triangle T(n,k), n >= 2, 0 <= k <= floor(n^2/2)-2*n+2, read by rows, where T(n,k) is the number of 2*(k+2*n-2)-cycles in the n X n grid graph which pass through NW and SE corners ((0,0),(n-1,n-1)).at n=21A333667