72075

Appears in sequences

• Odd numbers k that divide phi(k)*sigma(k).at n=31A015706
• Denominators of continued fraction convergents to sqrt(163).at n=12A041301
• Composite numbers k+1 such that k*phi(k+1) is a perfect square.at n=37A069068
• Nonnegative values x of solutions (x, y) to the Diophantine equation x^2+(x+217)^2 = y^2.at n=32A198294