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 A227770 #11 Jul 31 2013 14:56:43 %S A227770 5,7,11,19,31,59,113,223,443,883,1759,3511,7019,14033,28057,56101, %T A227770 112199,224363,448703,897401,1794787,3589571,7179127,14358247, %U A227770 28716487,57432961,114865903,229731787,459463553,918927083,1837854119,3675708217,7351416419,14702832827,29405665651,58811331281,117622662557,235245325061,470490650107,940981300211,1881962600417 %N A227770 Bertrand primes II: a(n) is the largest prime < 2*a(n-1)-2. %C A227770 A strong form of Bertrand's postulate (Chebyshev's theorem) says there exists a prime number p with n < p < 2*n - 2 if n > 3. %C A227770 The first prime > 3 is 5, so the sequence begins a(1) = 5. %C A227770 For references, links, and crossrefs, see A006992 (Bertrand primes I). %e A227770 The largest prime < 2*a(1)-2 = 2*5-2 = 8 is 7, so a(2) = 7 = A006992(4). %e A227770 The largest prime < 2*a(2)-2 = 2*7-2 = 12 is 11, so a(3) = 11 < 13 = A006992(5). %t A227770 NestList[NextPrime[2 # - 2, -1] &, 5, 40] %Y A227770 Cf. A006992. %K A227770 nonn %O A227770 1,1 %A A227770 _Jonathan Sondow_, Jul 30 2013