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 A049759 #25 Sep 08 2022 08:44:58
%S A049759 0,0,0,0,1,0,0,0,1,0,0,1,1,1,0,0,0,0,0,1,0,0,1,1,1,4,1,0,0,0,1,0,4,4,
%T A049759 1,0,0,1,0,1,1,3,4,1,0,0,0,1,0,0,4,2,4,1,0,0,1,1,1,1,1,2,1,4,1,0,0,0,
%U A049759 0,0,4,0,4,0,0,4,1,0,0,1,1,1,4,1,1,1,7,9,4,1,0
%N A049759 Triangular array T read by rows: T(n,k)=n^2 mod k, for k=1,2,...,n, n=1,2,...
%H A049759 G. C. Greubel, <a href="/A049759/b049759.txt">Rows n = 1..100 of triangle, flattened</a>
%e A049759 Triangle begins:
%e A049759 0;
%e A049759 0, 0;
%e A049759 0, 1, 0;
%e A049759 0, 0, 1, 0;
%e A049759 0, 1, 1, 1, 0;
%e A049759 0, 0, 0, 0, 1, 0;
%e A049759 0, 1, 1, 1, 4, 1, 0;
%e A049759 0, 0, 1, 0, 4, 4, 1, 0;
%e A049759 0, 1, 0, 1, 1, 3, 4, 1, 0;
%e A049759 0, 0, 1, 0, 0, 4, 2, 4, 1, 0;
%e A049759 0, 1, 1, 1, 1, 1, 2, 1, 4, 1, 0;
%e A049759 0, 0, 0, 0, 4, 0, 4, 0, 0, 4, 1, 0;
%e A049759 0, 1, 1, 1, 4, 1, 1, 1, 7, 9, 4, 1, 0;
%p A049759 seq(seq( `mod`(n^2, k), k = 1..n), n = 1..15); # _G. C. Greubel_, Dec 13 2019
%t A049759 Table[PowerMod[n,2,k], {n,15}, {k,n}]//Flatten (* _G. C. Greubel_, Dec 13 2019 *)
%o A049759 (PARI) tabl(nn) = {for (n=1, nn, for (k=1, n, print1(n^2 % k, ", ");); print(););} \\ _Michel Marcus_, Mar 31 2014
%o A049759 (Magma) [[Modexp(n,2,k): k in [1..n]]: n in [1..15]]; // _G. C. Greubel_, Dec 13 2019
%o A049759 (Sage) [[power_mod(n,2,k) for k in (1..n)] for n in (1..15)] # _G. C. Greubel_, Dec 13 2019
%o A049759 (GAP) Flat(List([1..15], n-> List([1..n], k-> PowerMod(n,2,k) ))); # _G. C. Greubel_, Dec 13 2019
%Y A049759 Cf. A048152.
%K A049759 nonn,tabl
%O A049759 1,26
%A A049759 _Clark Kimberling_