640640

Appears in sequences

• a(n) is the least integer that can be expressed as the difference of two octagonal numbers in exactly n ways.at n=19A334037
• Numbers k for which k * gcd(sigma(k), A003961(k)) is equal to sigma(k) * gcd(k, A003961(k)), where A003961 shifts the prime factorization one step towards larger primes, and sigma is the sum of divisors function.at n=8A349745