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 A128055 #16 Jan 05 2025 13:38:09
%S A128055 1,1,2,4,8,32,64,64,128,256,512,2048,4096,4096,8192,16384,32768,
%T A128055 131072,262144,262144,524288,1048576,2097152,8388608,16777216,
%U A128055 16777216,33554432,67108864,134217728,536870912,1073741824
%N A128055 a(n) = 2^A128054(n).
%C A128055 A factor in A128056.
%C A128055 The signed sequence 1,1,2,-4,-8,-32,-64,-64,-128,256,512... is the Hankel transform of the doubled sequence 1,1,2,2,6,6,... of central binomial coefficients (A128014). - _Paul Barry_, Sep 09 2008
%H A128055 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (2,-4,8,-16,32).
%F A128055 G.f.: (-1-16*x^4+4*x^3-4*x^2+x)/((2*x-1)*(4*x^2-2*x+1)*(4*x^2+2*x+1)). - Maksym Voznyy (voznyy(AT)mail.ru), Aug 11 2009
%F A128055 Sum_{n>=0} 1/a(n) = 62/21. - _Amiram Eldar_, Mar 28 2023
%t A128055 LinearRecurrence[{2,-4,8,-16,32},{1,1,2,4,8},31] (* _James C. McMahon_, Jan 05 2025 *)
%Y A128055 Cf. A128014, A128054, A128056.
%K A128055 easy,nonn
%O A128055 0,3
%A A128055 _Paul Barry_, Feb 13 2007