A256238 Number of primes in A256237 less than 10^n.

0, 1, 6, 68, 847, 7963, 81327, 800270, 7836076

Offset: 3

Author

Arkadiusz Wesolowski, Mar 20 2015

Keywords

• nonn
• more

Comments

Up to 10^9, primes congruent to 2 or 3 mod 5 appear in A256237 more often (42358 such primes) than primes congruent to 1 or 4 mod 5 (38969 such primes). Why?

Crossrefs

Cf. A254248, A255816, A255971, A256164, A256237.

Programs

PARI

isA256163(m) = if(!(m % 2), 0, my(pow = 2); while(pow < m && !isprime(m - pow) && !isprime(m + pow) && !isprime(m*pow - 1) && !isprime(m*pow + 1), pow *= 2); pow > m);
list(len) = {my(pow = 1000, c = 0); forprime(p = 1, 10^len, if(p > pow, print1(c, ", "); pow *= 10); if(isA256163(p), c++));} \\ Amiram Eldar, Jul 19 2025

Extensions

a(10)-a(11) from Amiram Eldar, Jul 19 2025