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 A087100 #8 Feb 02 2021 21:08:10
%S A087100 0,1,11,3,22,7,33,15,44,31,55,63,66,127,77,255,88,511,99,1023,110,
%T A087100 2047,121,4095,132,8191,143,16383,154,32767,165,65535,176,131071,187,
%U A087100 262143,198,524287,209,1048575,220,2097151,231,4194303,242,8388607,253
%N A087100 A000225 (2^n - 1) interlaced with A008593 (11n).
%H A087100 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,4,0,-5,0,2).
%F A087100 From _Chai Wah Wu_, Feb 02 2021: (Start)
%F A087100 a(n) = 4*a(n-2) - 5*a(n-4) + 2*a(n-6) for n > 5.
%F A087100 G.f.: x*(22*x^3 + x^2 - 11*x - 1)/((x - 1)^2*(x + 1)^2*(2*x^2 - 1)). (End)
%t A087100 Rest[With[{nn=30},Riffle[2^Range[0,nn]-1,11Range[0,nn]]]] (* _Harvey P. Dale_, Aug 15 2011 *)
%Y A087100 Cf. A063914, A087098, A086848.
%K A087100 easy,nonn
%O A087100 0,3
%A A087100 _Jeremy Gardiner_, Aug 10 2003