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 A174100 #10 May 19 2019 12:46:03 %S A174100 1,2,3,5,6,11,18,21,23,26,30,33,35,51,56,63,68,81,83,90,95,96,105,125, %T A174100 128,131,135,138,146,153,156,165,168,173,186,200,215,216,221,230,233, %U A174100 243,245,261,270,278,293,296,300,336,338,363,375,378,380,398 %N A174100 Numbers k such that both 2*k + 1 and 6*k + 1 are prime. %e A174100 a(1)=1 because 1*2 + 1 = 3 (a prime) and 1*6 + 1 = 7 (also a prime). %t A174100 Select[Range[400],PrimeQ[2#+1]&&PrimeQ[6#+1]&] (* _Harvey P. Dale_, Jan 17 2011 *) %Y A174100 Cf. A002476, A065091. %K A174100 nonn %O A174100 1,2 %A A174100 _Juri-Stepan Gerasimov_, Mar 07 2010 %E A174100 Corrected (118 removed, 132 replaced by 131) by _R. J. Mathar_, Apr 20 2010 %E A174100 Name edited by _Jon E. Schoenfield_, May 19 2019