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 A105575 #11 Sep 23 2017 20:20:19
%S A105575 5,11,17,23,29,31,41,47,53,59,61,71,73,83,89,101,107,113,131,137,139,
%T A105575 149,151,157,167,173,179,181,191,197,199,211,227,233,239,241,251,257,
%U A105575 263,269,271,281,283,293,311,317,331,337,347,353,359,367,373,383,389
%N A105575 Largest primes < numbers of the form 6k (duplicates removed).
%e A105575 11 is in the sequence because 11 is the largest prime < 12 = 6*2.
%t A105575 PrevPrim[n_] := Block[{k = n - 1}, While[ !PrimeQ[k], k-- ]; k]; Union[ Table[ PrevPrim[6n], {n, 65}]] (* _Robert G. Wilson v_, May 21 2005 *)
%t A105575 NextPrime[#,-1]&/@(6*Range[100])//Union (* _Harvey P. Dale_, Sep 23 2017 *)
%Y A105575 Cf. A105399.
%K A105575 easy,nonn
%O A105575 1,1
%A A105575 _Giovanni Teofilatto_, May 03 2005
%E A105575 Corrected and extended by _Robert G. Wilson v_, May 21 2005
%E A105575 Edited, corrected and extended by _Ray Chandler_, Oct 17 2006