|
%I #21 Jun 26 2017 05:10:51
%S 8569,39689,321265,430199,564719,585311,608399,7056721,11255201,
%T 17966519,18996769,74775791,75669551,136209151,321239359,446660929,
%U 547674049,866223359,1068433631,1227804929,1291695119,2315403649,2585930689,7229159729,7809974369,8117634239
%N Squarefree composite numbers n such that p^2 - 1 divides n^2 - 1 for every prime p dividing n.
%C Such numbers are odd and have at least three prime factors.
%C Problem: are there infinitely many such numbers?
%H Giovanni Resta, <a href="/A287119/b287119.txt">Table of n, a(n) for n = 1..50</a>
%o (PARI) isok(n) = {if (issquarefree(n) && !isprime(n), my(f = factor(n)); for (k=1, #f~, if ((n^2-1) % (f[k,1]^2-1), return (0));); return (1););} \\ _Michel Marcus_, May 20 2017
%Y Cf. A002997, A006972, A175530, A175531.
%Y Subsequence of A120944.
%K nonn
%O 1,1
%A _Thomas Ordowski_, May 20 2017
%E More terms from _Michel Marcus_, May 20 2017
%E a(14)-a(26) from _Giovanni Resta_, May 20 2017
|
