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 A139292 #8 Apr 11 2022 17:58:59 %S A139292 1,4,64,1024,262144,4194304,1073741824,17179869184,4398046511104, %T A139292 18014398509481984,288230376151711744,1180591620717411303424, %U A139292 302231454903657293676544,4835703278458516698824704 %N A139292 2^(2p - 1)/8, where p is prime. %F A139292 a(n) = A139286(n)/8. %t A139292 2^(2#-1)/8&/@Prime[Range[20]] (* _Harvey P. Dale_, Aug 19 2012 *) %Y A139292 Cf. A139286, A139287, A139288, A139289, A139290, A139291, A139293, A139294, A139306. %K A139292 nonn %O A139292 1,2 %A A139292 _Omar E. Pol_, Apr 13 2008 %E A139292 More terms from _Jon E. Schoenfield_, Jul 16 2010