136213

Appears in sequences

• Numbers k such that sigma(sigma(k)) == phi(k) (mod sigma(k)).at n=26A067204
• Numbers n for which phi(n)=sigma(n'), where phi is the Euler totient function, sigma is the sum of divisors and n' the arithmetic derivative of n.at n=15A189057
• Number of nXn 0..1 arrays with every element unequal to 0, 1 or 2 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=12A317758