a(n) is the number of n X n matrices of 0's, 1's and -1's in which the entries in each row or column sum to 1.

A050204

a(n) is the number of n X n matrices of 0's, 1's and -1's in which the entries in each row or column sum to 1.

Terms

    a(0) =1a(1) =2a(2) =21a(3) =1344a(4) =628080a(5) =2030271480

External references