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 A375747 #8 Sep 20 2024 06:39:14
%S A375747 3,2,1,-1,-2,4,3,2,1,-1,-2,-3,5,4,3,2,1,-1,-2,-3,-4,6,5,4,3,2,1,-1,-2,
%T A375747 -3,-4,-5,7,6,5,4,3,2,1,-1,-2,-3,-4,-5,-6,8,7,6,5,4,3,2,1,-1,-2,-3,-4,
%U A375747 -5,-6,-7,9,8,7,6,5,4,3,2,1,-1,-2,-3,-4,-5,-6,-7,-8
%N A375747 Table read by rows: T(n,k) for n >= 3 and k=1,2,...,2*n-1 are the distinct eigenvalues of the twisted odd graph O^(sigma)_n.
%H A375747 Miquel A. Fiol, E. Garriga, and J. L. A. Yebra, <a href="https://doi.org/10.1017/S0963548300004181">On twisted odd graphs</a>, Combin. Probab. Comput. 9 (2000), 227-240.
%F A375747 T(n,1) = n; T(n,k) = n+1-k for k=2,...,n; T(n,k) = n-k for k=n+1,...,2n-1.
%e A375747 The table begins:
%e A375747 3 2 1 -1 -2
%e A375747 4 3 2 1 -1 -2 -3
%e A375747 5 4 3 2 1 -1 -2 -3 -4
%e A375747 6 5 4 3 2 1 -1 -2 -3 -4 -5
%e A375747 7 6 5 4 3 2 1 -1 -2 -3 -4 -5 -6
%e A375747 ...
%t A375747 T[n_,k_]:=If[k==1, n, If[1<k<=n, n+1-k, n-k]]; Flatten[Table[T[n,k],{n,3,9},{k,2n-1}]] (* _Stefano Spezia_, Aug 27 2024 *)
%Y A375747 Cf. A001700.
%K A375747 tabf,easy,sign
%O A375747 3,1
%A A375747 _Miquel A. Fiol_, Aug 26 2024