233740

Appears in sequences

• Number of primitive (period n) periodic palindromes using a maximum of five different symbols.at n=13A056496
• 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=21A069552
• Numbers n such that sigma(n) = 7*phi(n).at n=18A136540
• a(n) is the number of squares of side length greater than 1 having vertices at the points of an n X n grid of dots.at n=40A328152
• Numbers k such that sigma(k) = psi(k) + phi(k).at n=31A389478