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 A160417 #10 Feb 03 2024 10:16:43
%S A160417 2,1,7,1,7,3,21,1,7,3,21,3,21,9,63,1,7,3,21,3,21,9,63,3,21,9,63,9,63,
%T A160417 27,189,1,7,3,21,3,21,9,63,3,21,9,63,9,63,27,189,3,21,9,63,9,63,27,
%U A160417 189,9,63,27,189,27,189,81,567,1,7,3,21,3,21,9,63,3,21
%N A160417 a(n) = A160415(n+1)/4.
%t A160417 With[{d = 2}, wt[n_] := DigitCount[n, 2, 1]; f[n_] := If[OddQ[n], 3^d + (2^d) * Sum[(2^d - 1)^(wt[k] - 1), {k, 1, (n - 1)/2}] + (2^d)*(3^d - 2) * Sum[(2^d - 1)^(wt[k] - 1), {k, 1, (n - 3)/2}], 3^d + (2^d) * Sum[(2^d - 1)^(wt[k] - 1), {k, 1, n/2 - 1}] + (2^d)*(3^d - 2) * Sum[(2^d - 1)^(wt[k] - 1), {k, 1, n/2 - 1}]]; f[0] = 0; f[1] = 1; Differences[Array[f, 100]]/4] (* _Amiram Eldar_, Feb 02 2024 *)
%Y A160417 Cf. A152978, A160118, A160413, A160415.
%K A160417 nonn
%O A160417 1,1
%A A160417 _Omar E. Pol_, Jun 13 2009
%E A160417 More terms from _Max Alekseyev_, Dec 12 2011
%E A160417 More terms from _Amiram Eldar_, Feb 02 2024