A107747 Numbers k such that the least prime factor of 6*k+1 < the least prime factor of 6*k-1, A107744(k) < A107745(k).

4, 8, 9, 14, 15, 19, 22, 24, 28, 29, 34, 39, 42, 43, 44, 49, 50, 53, 54, 57, 59, 60, 64, 65, 67, 69, 74, 75, 78, 79, 80, 82, 84, 85, 89, 92, 93, 94, 98, 99, 104, 108, 109, 113, 114, 117, 119, 120, 124, 127, 129, 130, 133, 134, 139, 140, 144, 148, 149, 150, 152, 154

Offset: 1

Author

Zak Seidov, May 23 2005

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A107744 (smallest prime factor of 6*n+1), A107745 (smallest prime factor of 6*n-1), A107746 (values of k such that A107744(k) > A107745(k)).

Programs

Mathematica

lpfQ[n_]:=Module[{c=6n},FactorInteger[c+1][[1,1]] < FactorInteger [c-1][[1,1]]]; Select[Range[200],lpfQ] (* Harvey P. Dale, Apr 18 2011 *)

PARI

isok(n) = vecmin(factor(6*n+1)[, 1]) < vecmin(factor(6*n-1)[, 1]);
for(n=1, 200,if(isok(n)==1, print1(n", "))) \\ Altug Alkan, Oct 23 2015

Extensions

Comments corrected and (at the suggestion of Michel Marcus) moved to Crossrefs by Jason Kimberley, Oct 23 2015