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 A325743 #4 Jun 06 2019 22:00:27
%S A325743 0,1,-1,1,-2,6,-16,36,-71,126,-201,276,-276,0,1014,-3744,10179,-24309,
%T A325743 54126,-115614,240444,-490104,980209,-1918752,3658449,-6750224,
%U A325743 11950524,-20058300,31303782,-43733304,49586229,-28048799,-67798986,331797126,-932095976
%N A325743 First term of n-th difference sequence of (floor(Pi*k/4)), k >= 0.
%H A325743 Clark Kimberling, <a href="/A325743/b325743.txt">Table of n, a(n) for n = 1..200</a>
%t A325743 Table[First[Differences[Table[Floor[(Pi/4)*n], {n, 0, 50}], n]], {n, 1, 50}]
%Y A325743 Cf. A003881, A325664.
%K A325743 easy,sign
%O A325743 1,5
%A A325743 _Clark Kimberling_, Jun 06 2019