%I #10 Jun 20 2024 02:37:23

%S 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 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 0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

%N Characteristic sequence for the Pell numbers.

%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>.

%F G.f.: Sum_{k>=0} x^A000129(k).

%t a[n_] := If[Or @@ (IntegerQ[Sqrt[#]]& /@ (2*n^2 + {-1, 1})), 1, 0]; Array[a, 100, 0] (* _Amiram Eldar_, Jun 20 2024 *)

%Y Cf. A000129.

%K easy,nonn

%O 0,1

%A _Paul Barry_, Apr 01 2005