Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to 3 up to permutations of rows and columns.

A333888

Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to 3 up to permutations of rows and columns.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =5a(4) =12a(5) =29a(6) =79a(7) =225a(8) =677a(9) =2141a(10) =7121a(11) =24693a(12) =89117a(13) =333312a(14) =1288949a(15) =5140039a(16) =21094565a(17) =88931387a(18) =384544989a(19) =1703083332a(20) =7715920544a(21) =35720666818a(22) =168809971994a(23) =813633173238

External references