Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to 4 up to permutations of rows and columns.

A333889

Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to 4 up to permutations of rows and columns.

Terms

    a(0) =1a(1) =1a(2) =3a(3) =9a(4) =33a(5) =142a(6) =742a(7) =4454a(8) =30516a(9) =233574a(10) =1972430a(11) =18190806a(12) =181774873a(13) =1955268162a(14) =22516241557a(15) =276294103003

External references