1402440

Appears in sequences

• a(n) = 2*(3*n)! / ((2*n+1)!*(n+1)!).at n=11A000139
• Numbers k such that sigma(k) = phi(k)*(sum of the digits of k).at n=7A140173
• Numbers n such that sigma(n) = 15*phi(n) (where sigma=A000203, phi=A000010).at n=21A171260