A275631 - OEIS

A275631

Primes p such that the product of the distinct prime factors of p^2-1 is less than p.

%I #18 Apr 10 2017 17:21:52

%S 3,7,17,31,97,127,251,449,487,577,1151,1249,1567,1999,2663,4801,4999,

%T 7937,8191,12799,13121,13183,15551,31249,31751,32257,33857,35153,

%U 39367,65537,79201,81919,85751,115249,117127,124001,126001,131071

%N Primes p such that the product of the distinct prime factors of p^2-1 is less than p.

%H Dana Jacobsen, <a href="/A275631/b275631.txt">Table of n, a(n) for n = 1..340</a>

%t Select[Prime[Range[13000]],Times@@FactorInteger[#^2-1][[All,1]]<#&] (* _Harvey P. Dale_, Apr 10 2017 *)

%o (Perl) use ntheory ":all"; forprimes { say if vecprod(map { $_->[0] } factor_exp($_**2-1)) < $_ } 1e6; # _Dana Jacobsen_, Aug 09 2016

%Y Cf. A007947, A275630.

%K nonn

%O 1,1

%A _N. J. A. Sloane_, Aug 07 2016, following a suggestion from _J. M. Bergot_.

%E Terms a(10) and beyond from _Dana Jacobsen_, Aug 09 2016