499194

Appears in sequences

• Number of n X n symmetric matrices with nonnegative integer entries, trace 0 and all row sums 2.at n=10A002137
• Triangle read by rows: T(n,k) is the number of multigraphs without loops on n labeled nodes with k edges and maximum degree 2.at n=53A095693
• Array read by antidiagonals: T(n,k) is the number of k-regular loopless multigraphs on n labeled nodes, n >= 0, k >= 0.at n=88A333351