A339347 Primes p such that p < (gpf((p - 1)/gpf(p - 1)))^4, where gpf(k) is the greatest prime factor of k, A006530.

5, 7, 11, 13, 19, 31, 37, 43, 61, 67, 71, 73, 79, 101, 131, 151, 191, 197, 211, 239, 251, 281, 311, 331, 401, 419, 421, 431, 443, 461, 463, 491, 521, 547, 571, 599, 601, 617, 647, 659, 677, 683, 727, 743, 827, 859, 883, 911, 947, 953, 967, 1013, 1093, 1103

Offset: 1

Author

Peter Luschny, Dec 13 2020

Keywords

• nonn

Comments

Inspired by A339466. See the references there.

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A006530, A339466.

Programs

Maple

alias(pf = NumberTheory:-PrimeFactors): gpf := n -> max(pf(n)):
is_a := n -> isprime(n) and n < (gpf((n-1)/gpf(n-1)))^4:
select(is_a, [$5..1150]);

PARI

gpf(n) = if (n==1, 1, vecmax(factor(n)[, 1])); \\ A006530
isok(p) = isprime(p) && (p < (gpf((p - 1)/gpf(p - 1)))^4); \\ Michel Marcus, Dec 14 2020