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 A129098 #8 Mar 10 2020 15:32:48
%S A129098 1,5,23,135,1119,14319,300015,10636463,652217135,70382845743,
%T A129098 13551477257519,4706105734658351,2973879284783561007,
%U A129098 3444999327807280048431,7362415635261959807011119,29188908702092573515760044335
%N A129098 a(n) = A129095(2^n + 2^(n-1) - 1) for n>=1.
%C A129098 b(n)=A129095(n) obeys the recurrence: b(n) = b(n/2) (n even), b(n) = 2*b(n-1) + b(n-2) (n odd >1), with b(1) = 1.
%t A129098 Block[{e = 18, s}, s = Nest[Append[#1, If[EvenQ[#2], #1[[#2/2]], 2 #1[[-1]] + #1[[-2]] ] ] & @@ {#, Length@ # + 1} &, {1}, 2^e]; Array[s[[2^# + 2^(# - 1) - 1]] &, e - 1]] (* _Michael De Vlieger_, Mar 10 2020 *)
%o A129098 (PARI)
%Y A129098 Cf. A129095, A129096, A129097, A129099.
%K A129098 easy,nonn
%O A129098 1,2
%A A129098 _Paul D. Hanna_, Apr 11 2007
%E A129098 a(16) from _Michael De Vlieger_, Mar 10 2020.