91514domain: NAppears in sequencesa(n) = floor((-1)^n*n!*(E(n,2)-E(n,1)*E(n-1,1))) where E(n,x) = Sum_{k=0..n} (-1)^k*x^k/k!.at n=20A065955a(n) is the number of ways to partition {1,2,...,n} into two sets X and Y such that the sum of the elements of each is a square.at n=25A374087