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 A325673 #9 Feb 20 2022 08:18:01
%S A325673 -3,0,1,-3,6,-9,9,0,-27,81,-162,243,-243,0,729,-2187,4375,-6579,6732,
%T A325673 -1139,-13719,32946,-18921,-158355,851598,-2896919,8097219,-20058300,
%U A325673 45540943,-96506229,193012458,-367077447,667617642,-1166803109,1968991969,-3225375252
%N A325673 First term of n-th difference sequence of (floor(k*r)), r = -sqrt(7), k >= 0.
%H A325673 Clark Kimberling, <a href="/A325673/b325673.txt">Table of n, a(n) for n = 1..200</a>
%t A325673 Table[First[Differences[Table[Floor[-Sqrt[7]*n], {n, 0, 30}], n]], {n, 0, 50}]
%Y A325673 Cf. A022841, A325664, A325672.
%K A325673 easy,sign
%O A325673 1,1
%A A325673 _Clark Kimberling_, May 15 2019