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 A185231 #19 Jul 09 2025 04:32:51
%S A185231 1,2,3,5,7,13,23,43,83,163,317,631,1259,2503,5003,9973,19937,39869,
%T A185231 79699,159389,318751,637499,1274989,2549951,5099893,10199767,20399531,
%U A185231 40799041,81598067,163196129,326392249,652784471,1305568919,2611137817
%N A185231 a(n) = largest prime <= 2a(n-1), with a(0)=1.
%C A185231 Equals 1 followed by A006992.
%C A185231 This is a complete sequence (cf. A075058).
%H A185231 Harvey P. Dale, <a href="/A185231/b185231.txt">Table of n, a(n) for n = 0..1000</a>
%t A185231 np[n_]:=Module[{p=NextPrime[2n]},If[p<=2n,p,NextPrime[p,-1]]]; NestList[ np,1,40] (* _Harvey P. Dale_, Sep 29 2019 *)
%o A185231 (PARI) lista(nn) = {p = 1; for (n = 1, nn, print1(p, ", "); p = precprime(2*p););} \\ _Michel Marcus_, Aug 26 2013
%Y A185231 Cf. A006992, A075058.
%K A185231 nonn
%O A185231 0,2
%A A185231 _N. J. A. Sloane_, Jan 24 2012, following a suggestion from Frank M Jackson