Number of n X n symmetric matrices with nonnegative integer entries, trace 0 and all row sums 2.
A002137
Number of n X n symmetric matrices with nonnegative integer entries, trace 0 and all row sums 2.
Terms
- a(0) =1a(1) =0a(2) =1a(3) =1a(4) =6a(5) =22a(6) =130a(7) =822a(8) =6202a(9) =52552a(10) =499194a(11) =5238370a(12) =60222844a(13) =752587764a(14) =10157945044a(15) =147267180508
External references
- oeis: A002137