This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A256238 #22 Jul 19 2025 10:12:53
%S A256238 0,1,6,68,847,7963,81327,800270,7836076
%N A256238 Number of primes in A256237 less than 10^n.
%C A256238 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?
%o A256238 (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);
%o A256238 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
%Y A256238 Cf. A254248, A255816, A255971, A256164, A256237.
%K A256238 nonn,more
%O A256238 3,3
%A A256238 _Arkadiusz Wesolowski_, Mar 20 2015
%E A256238 a(10)-a(11) from _Amiram Eldar_, Jul 19 2025