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 A216309 #19 Dec 01 2018 12:23:00
%S A216309 181,211,241,421,631,661,691,811,1021,1051,1171,1201,1381,1471,1511,
%T A216309 1531,1801,1811,1831,1951,2161,2221,2251,2311,2521,2621,2731,2861,
%U A216309 2971,3001,3121,3191,3271,3331,3361,3391,3571,3931,4111,4201,4231,4261,4621,4691
%N A216309 The prime ending in 1 is the only prime in a decade.
%C A216309 Primes of the form 10n+1 such that 10n+3, 10n+7, and 10n+9 are composite. - _Charles R Greathouse IV_, Sep 06 2012
%H A216309 V. Raman, <a href="/A216309/b216309.txt">Table of n, a(n) for n = 1..10000</a>
%F A216309 a(n) ~ 4n log n. - _Charles R Greathouse IV_, Sep 06 2012
%t A216309 t = {}; Do[ps = Select[Range[10*n, 10*n + 9], PrimeQ]; If[ps == {10*n + 1}, AppendTo[t, ps[[1]]]], {n, 0, 588}]; t (* _T. D. Noe_, Sep 04 2012 *)
%t A216309 Select[10*Range[500]+1,PrimeQ[#]&&AllTrue[#+{2,6,8},CompositeQ]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Dec 01 2018 *)
%Y A216309 Subsequence of A030430. Cf. A032352, A007811, A078494.
%K A216309 nonn,base,easy
%O A216309 1,1
%A A216309 _V. Raman_, Sep 03 2012