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 A031215 #41 Sep 08 2022 08:44:50
%S A031215 3,7,13,19,29,37,43,53,61,71,79,89,101,107,113,131,139,151,163,173,
%T A031215 181,193,199,223,229,239,251,263,271,281,293,311,317,337,349,359,373,
%U A031215 383,397,409,421,433,443,457,463,479,491,503,521,541,557,569
%N A031215 Even-indexed primes: a(n) = prime(2n).
%C A031215 Also every second odd prime. - _Cino Hilliard_, Dec 02 2007
%C A031215 If n > 1, then a(n) is less than, and asymptotic to, the n-th Ramanujan prime R_n = A104272(n). Research questions on the difference R_n - a(n) are at A104272. - _Jonathan Sondow_, Dec 16 2013
%H A031215 Jens Kruse Andersen, <a href="/A031215/b031215.txt">Table of n, a(n) for n = 1..10000</a>
%F A031215 a(n) = A104272(n) - A233739(n). - _Jonathan Sondow_, Dec 16 2013
%F A031215 a(n) = A105720(n) - A161463(n). - _Torlach Rush_, May 31 2021
%p A031215 A031215 := n->ithprime(2*n);
%t A031215 Table[ Prime[ 2n], {n, 52}] (* _Robert G. Wilson v_, Dec 01 2013 *)
%o A031215 (Magma) [ NthPrime(2*n): n in [1..1000] ]; // _Vincenzo Librandi_, Apr 11 2011
%o A031215 (PARI) a(n)=prime(2*n) \\ _Charles R Greathouse IV_, Jul 02 2013
%Y A031215 Cf. A000040, A031368 (odd-indexed primes), A104272, A105720, A161463, A179740, A233739.
%K A031215 nonn,easy
%O A031215 1,1
%A A031215 _Jeff Burch_