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 A381233 #10 Mar 01 2025 16:45:27
%S A381233 0,0,1,-1,0,1,-1,2,-2,0,1,-1,2,-2,3,-3,0,1,-1,2,-2,3,-3,4,-4,0,1,-1,2,
%T A381233 -2,3,-3,4,-4,5,-5,0,1,-1,2,-2,3,-3,4,-4,5,-5,6,-6,0,1,-1,2,-2,3,-3,4,
%U A381233 -4,5,-5,6,-6,7,-7,0,1,-1,2,-2,3,-3,4,-4,5,-5,6,-6,7,-7,8,-8,0,1,-1,2,-2,3,-3,4,-4,5,-5,6,-6,7,-7,8,-8,9,-9
%N A381233 Concatenate the sequences S(k) = [0, 1, -1, ..., k, -k] for k = 0, 1, ...
%H A381233 Paolo Xausa, <a href="/A381233/b381233.txt">Table of n, a(n) for n = 0..10200</a> (k = 0..100)
%t A381233 Flatten[Table[(-1)^j*Floor[j/2], {k, 0, 10}, {j, 2*k + 1}]] (* _Paolo Xausa_, Mar 01 2025 *)
%Y A381233 Cf. A196199, A381232.
%K A381233 sign,easy
%O A381233 0,8
%A A381233 _N. J. A. Sloane_, Mar 01 2025 [Suggested by _Franklin T. Adams-Watters_, Sep 21 2011]