278513

Appears in sequences

• Numbers k such that sigma(phi(sigma(k))) = phi(sigma(phi(k))).at n=36A067160
• Number of non-intersecting cycle systems in a particular directed graph.at n=9A112831
• a(n) = -a(n-1) + 3*a(n-2), starting a(1)=1, a(2)=2.at n=17A140165