522522

Appears in sequences

• a(n) = (1)*(2 + 3 + 4 + ... + n) + (1 + 2)*(3 + 4 + 5 + ... + n) + (1 + 2 + 3)*(4 + 5 + 6 + ... + n) + ... + (1 + 2 + 3 + ... + n-1)*n.at n=26A067056
• Numbers k such that phi(k) = sigma(core(k)) where phi(k) is the Euler totient function, sigma(k) the sum of divisors of k and core(k) the squarefree part of k (the smallest integer such that k*core(k) is a square).at n=26A069552
• Numbers n such that sigma(n) = 13*phi(n) (where sigma=A000203, phi=A000010).at n=16A171258
• Numbers k such that sigma(k) = psi(k) + phi(k).at n=40A389478