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 A115357 #20 Dec 14 2023 05:30:59
%S A115357 1,1,1,0,2,0,1,1,1,0,2,0,1,1,1,0,2,0,1,1,1,0,2,0,1,1,1,0,2,0,1,1,1,0,
%T A115357 2,0,1,1,1,0,2,0,1,1,1,0,2,0,1,1,1,0,2,0,1,1,1,0,2,0,1,1,1,0,2,0,1,1,
%U A115357 1,0,2,0
%N A115357 Period 6: repeat [1,1,1,0,2,0].
%C A115357 Diagonal sums of number triangle A115356.
%H A115357 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (-1,0,1,1).
%F A115357 G.f.: (1+2*x+2*x^2)/(1+x-x^3-x^4).
%F A115357 a(n) = -a(n-1)+a(n-3)+a(n-4).
%F A115357 a(n) = -cos(2*Pi*n/3+Pi/6)/sqrt(3)+sin(2*Pi*n/3+Pi/6)/3+(-1)^n/2+5/6.
%F A115357 Sequence shifted right by 2 is additive with a(p^e) = 1 if p = 2 or 3, 0 otherwise.
%t A115357 PadRight[{},120,{1,1,1,0,2,0}] (* or *) LinearRecurrence[{-1,0,1,1},{1,1,1,0},120] (* _Harvey P. Dale_, Jan 28 2015 *)
%Y A115357 Cf. A171182. [From _Juri-Stepan Gerasimov_, Dec 04 2009]
%Y A115357 Cf. A115356.
%K A115357 easy,nonn
%O A115357 0,5
%A A115357 _Paul Barry_, Jan 21 2006