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 A121290 #11 Jul 22 2017 08:32:26
%S A121290 0,1,5,85,341,5461,21845,349525,22369621,89478485,5726623061,
%T A121290 91625968981,366503875925,5864062014805,375299968947541,
%U A121290 24019198012642645,96076792050570581,6148914691236517205
%N A121290 a(n) = (2^prime(n) - 8)/24 for n>=2.
%C A121290 Previous name was: (2^(p-3) - 1)/3, where p is an odd prime, i.e., p = A065091.
%t A121290 Table[(2^Prime[n] - 8)/24, {n, 2, 100}] (* _Artur Jasinski_ *)
%Y A121290 Cf. A000043, A000668, A124477, A139479, A139480.
%K A121290 nonn,easy,less
%O A121290 1,3
%A A121290 _Lekraj Beedassy_, Aug 24 2006
%E A121290 New name from _Joerg Arndt_, Jul 21 2017