a(n) is the number of n X n matrices with nonnegative integer entries, row sums 1,2,...,n and column sums 1,2,...,n.

A361749

a(n) is the number of n X n matrices with nonnegative integer entries, row sums 1,2,...,n and column sums 1,2,...,n.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =12a(4) =261a(5) =22645a(6) =8264346a(7) =13150070522

External references