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Primes p such that p < (gpf((p - 1)/gpf(p - 1)))^4, where gpf(k) is the greatest prime factor of k, A006530.
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%I #17 Dec 15 2020 17:35:06

%S 5,7,11,13,19,31,37,43,61,67,71,73,79,101,131,151,191,197,211,239,251,

%T 281,311,331,401,419,421,431,443,461,463,491,521,547,571,599,601,617,

%U 647,659,677,683,727,743,827,859,883,911,947,953,967,1013,1093,1103

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

%C Inspired by A339466. See the references there.

%H Robert Israel, <a href="/A339347/b339347.txt">Table of n, a(n) for n = 1..10000</a>

%p alias(pf = NumberTheory:-PrimeFactors): gpf := n -> max(pf(n)):

%p is_a := n -> isprime(n) and n < (gpf((n-1)/gpf(n-1)))^4:

%p select(is_a, [$5..1150]);

%o (PARI) gpf(n) = if (n==1, 1, vecmax(factor(n)[, 1])); \\ A006530

%o isok(p) = isprime(p) && (p < (gpf((p - 1)/gpf(p - 1)))^4); \\ _Michel Marcus_, Dec 14 2020

%Y Cf. A006530, A339466.

%K nonn

%O 1,1

%A _Peter Luschny_, Dec 13 2020