1885129
domain: N
Appears in sequences
- Least square s such that A078142(s) is equal to the n-th prime.at n=19A076830
- Numbers k that require four iterations of the sigma function to be >= 2*k.at n=23A107914
- Odd numbers N for which numerator(sigma(N)/N) is a prime.at n=38A193065
- Numbers k such that tau(sigma(tau(k))) = sigma(tau(sigma(k))), where tau is A000005 and sigma is A000203.at n=33A237613
- Numbers n such that 2n-1 and sigma(n) are both primes.at n=21A249902
- Odd squares not of the form p + 2^k with p prime.at n=18A276567