Number of ways of partitioning the integers {1,2,..,4n-1} into two unordered sets such that the sums of parts are equal in both sets (parts in one of the sets hence sum up to n*(4n-1)). Number of solutions to {1 +- 2 +- 3+ ... +- 4n-1 = 0}.

A104456

Number of ways of partitioning the integers {1,2,..,4n-1} into two unordered sets such that the sums of parts are equal in both sets (parts in one of the sets hence sum up to n*(4n-1)). Number of solutions to {1 +- 2 +- 3+ ... +- 4n-1 = 0}.