This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A107745 #37 Nov 03 2024 02:03:58 %S A107745 5,11,17,23,29,5,41,47,53,59,5,71,7,83,89,5,101,107,113,7,5,131,137, %T A107745 11,149,5,7,167,173,179,5,191,197,7,11,5,13,227,233,239,5,251,257,263, %U A107745 269,5,281,7,293,13,5,311,317,17,7,5,11,347,353,359,5,7,13,383,389,5,401,11 %N A107745 Smallest prime factor of 6*n-1. %C A107745 If 6*n-1 is prime, a(n) = 6*n-1. %H A107745 Amiram Eldar, <a href="/A107745/b107745.txt">Table of n, a(n) for n = 1..10000</a> %F A107745 a(n) = A020639(6n-1). - _R. J. Mathar_, Jan 23 2007 %F A107745 5 <= a(n) <= 6n - 1; both bounds are sharp. - _Charles R Greathouse IV_, Sep 02 2024 %t A107745 a[n_]:= FactorInteger[6*n - 1][[1, 1]]; Array[a, 100] %o A107745 (PARI) vector(100, n, vecmin(factor(6*n-1)[, 1])) \\ _Altug Alkan_, Oct 23 2015 %o A107745 (Magma) [Min(PrimeFactors(6*n-1)):n in[1..68]]; // _Jason Kimberley_, Oct 28 2015 %Y A107745 Cf. A020639, A016969, A111863. %Y A107745 Cf. A107744 (smallest prime factor of 6*n+1), A107746 (values of k such that A107744(k) > A107745(k)), A107747 (values of k such that A107744(k) < A107745(k)). %K A107745 nonn,easy %O A107745 1,1 %A A107745 _Zak Seidov_, May 23 2005 %E A107745 Comments corrected and (at the suggestion of _Michel Marcus_) moved to Crossrefs by _Jason Kimberley_, Oct 23 2015