69450

Appears in sequences

• Triangle read by rows: T(n,k) gives number of r-bicoverings of an n-set with k blocks, n >= 2, k = 3..n+floor(n/2).at n=23A060052
• Triangle T(n, k) = the number of point-labeled graphs with n points and k edges, no points isolated, no edges isolated. By rows, 0 <= n, ceiling(2*n/3) <= k <= binomial(n, 2).at n=28A276640
• G.f.: Product_{m>0} (1+x^m+2!*x^(2*m)).at n=48A293204
• a(n) = Sum_{k=1..n-1} tau(k) * sigma_2(n-k).at n=38A374973