200413

Appears in sequences

• Numbers k such that sigma(phi(sigma(k))) = phi(sigma(phi(k))).at n=33A067160
• Numbers k such that (2*k-1)!! mod k! is greater than (2k+1)!! mod (k+1)!.at n=7A232863
• Triangle T(n,d) read by rows: the number of mixed trees with n>=1 nodes and 0<=d<n arcs.at n=51A335362