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 A105349 #10 Jun 20 2024 02:37:23
%S A105349 1,1,1,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,
%T A105349 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%U A105349 0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
%N A105349 Characteristic sequence for the Pell numbers.
%H A105349 <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>.
%F A105349 G.f.: Sum_{k>=0} x^A000129(k).
%t A105349 a[n_] := If[Or @@ (IntegerQ[Sqrt[#]]& /@ (2*n^2 + {-1, 1})), 1, 0]; Array[a, 100, 0] (* _Amiram Eldar_, Jun 20 2024 *)
%Y A105349 Cf. A000129.
%K A105349 easy,nonn
%O A105349 0,1
%A A105349 _Paul Barry_, Apr 01 2005