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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
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
1,1
LINKS
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 *)
PROG
(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
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)).
Sequence in context: A120512 A046954 A112775 * A121763 A110087 A312830
KEYWORD
nonn,changed
AUTHOR
Zak Seidov, May 23 2005
EXTENSIONS
Comments corrected and (at the suggestion of Michel Marcus) moved to Crossrefs by Jason Kimberley, Oct 23 2015
STATUS
approved