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 A064975 #9 Jul 15 2025 11:05:53 %S A064975 2,11,20,83,149,188,209,326,347,566,944,1301,1565,1574,1607,1805,1892, %T A064975 1943,2102,2228,2531,3173,3485,4379,5135,5534,6299,6722,6950,7223, %U A064975 7727,7970,8105,8273,8882,9785,9914,10112,10985,11654,11930,12221,13547 %N A064975 Numbers k such that 10*k-1, 10*k-3, 10*k-7 and 10*k-9 are all prime. %t A064975 Select[Range[10^5], PrimeQ[10# - 1] && PrimeQ[10# - 3] && PrimeQ[10# - 7] && PrimeQ[10# - 9] &] %Y A064975 Cf. A115095 (essentially the same). %K A064975 easy,nonn %O A064975 1,1 %A A064975 _Robert G. Wilson v_, Oct 30 2001