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 A091880 #15 Aug 26 2024 02:00:29
%S A091880 1,4,9,14,15,18,21,22,25,36,39,40,48,53,59,65,67,70,72,73,74,82,85,88,
%T A091880 99,101,110,114,122,125,127,129,130,137,143,146,147,155,158,168,174,
%U A091880 177,180,181,188,194,198,200,202,204,213,216,219,220,224,226,229,235
%N A091880 A049232 indexed by A000040.
%C A091880 The asymptotic density of this sequence is 1 - 2 * Product_{p prime} (1-1/(p*(p-1))) = 1 - 2 * A005596 = 0.252088... - _Amiram Eldar_, Feb 28 2021
%H A091880 Amiram Eldar, <a href="/A091880/b091880.txt">Table of n, a(n) for n = 1..10000</a>
%F A091880 a(n) = k such that A000040(k) = A049232(n).
%t A091880 Select[Range[100], ! SquareFreeQ[Prime[ # ] + 2] &] (* _Zak Seidov_, Oct 28 2008 *)
%Y A091880 Cf. A000040, A005596, A049232.
%K A091880 easy,nonn
%O A091880 1,2
%A A091880 _Ray Chandler_, Feb 15 2004