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 A097743 #23 Dec 12 2017 02:00:33
%S A097743 5,11,47,191,3071,12287,196607,786431,12582911,805306367,3221225471,
%T A097743 206158430207,3298534883327,13194139533311,211106232532991,
%U A097743 13510798882111487,864691128455135231,3458764513820540927
%N A097743 Numbers of the form 3*2^(p - 1) - 1 where p is prime.
%H A097743 Iain Fox, <a href="/A097743/b097743.txt">Table of n, a(n) for n = 1..467</a>
%F A097743 a(n) = A001348(n) + A061286(n). - _Iain Fox_, Dec 08 2017
%e A097743 p=2, 2^(2-1) + (2^2 - 1) = 5;
%e A097743 p=3, 2^(3-1) + (2^3 - 1) = 11.
%t A097743 Table[3*2^(Prime[n] - 1) - 1, {n, 18}] (* _Robert G. Wilson v_, Sep 24 2004 *)
%o A097743 (PARI) a(n) = 3*2^(prime(n) - 1) - 1; \\ _Michel Marcus_, Nov 30 2017
%Y A097743 Cf. A000396, A098102, A055010.
%K A097743 nonn
%O A097743 1,1
%A A097743 _Parthasarathy Nambi_, Sep 21 2004
%E A097743 Edited and extended by _Robert G. Wilson v_, Sep 24 2004