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 A374381 #7 Jul 12 2024 10:17:40
%S A374381 1,2,-1,1,-1,1,1,-1,-1,-1,1,1,1,2,1,2,-1,-2,-1,-1,-1,1,2,1,1,1,-1,1,2,
%T A374381 -1,-2,-1,1,-1,2,-1,1,-1,1,-2,1,-2,1,-1,1,1,-1,-1,-1,2,-1,1,-1,-1,-1,
%U A374381 1,1,1,2,1,2,1,1,1,2,1,2,-1,-2,-1,-1,-1,-2,-1,-2,-1,-1,-1
%N A374381 Triangle T(n, k), n > 0, k = 0..n-1, read by rows; T(n, k) = (n mod m) - (k mod m) where m = A007978(n-k).
%H A374381 Rémy Sigrist, <a href="/A374381/a374381.png">Scatterplot of (x, y) such that T(x, y) > 0 and x <= 420</a>
%F A374381 T(n, 0) = A213636(n).
%F A374381 T(n, n-1) = (-1)^(n-1).
%e A374381 Triangle T(n, k) begins:
%e A374381 n n-th row
%e A374381 -- ---------------------------------------------
%e A374381 1 1
%e A374381 2 2, -1
%e A374381 3 1, -1, 1
%e A374381 4 1, -1, -1, -1
%e A374381 5 1, 1, 1, 2, 1
%e A374381 6 2, -1, -2, -1, -1, -1
%e A374381 7 1, 2, 1, 1, 1, -1, 1
%e A374381 8 2, -1, -2, -1, 1, -1, 2, -1
%e A374381 9 1, -1, 1, -2, 1, -2, 1, -1, 1
%e A374381 10 1, -1, -1, -1, 2, -1, 1, -1, -1, -1
%e A374381 11 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1
%e A374381 12 2, -1, -2, -1, -1, -1, -2, -1, -2, -1, -1, -1
%o A374381 (PARI) T(n, k) = { for (m = 2, oo, my (d = (n%m) - (k%m)); if (d, return (d););); }
%Y A374381 Cf. A007978, A213636, A374369.
%K A374381 sign,base,easy,tabl
%O A374381 1,2
%A A374381 _Rémy Sigrist_, Jul 07 2024