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 A343720 #9 Feb 16 2025 08:34:02 %S A343720 0,0,1,0,1,1,0,1,0,1,0,1,4,4,1,0,1,4,3,4,1,0,1,4,2,2,4,1,0,1,4,1,0,1, %T A343720 4,1,0,1,4,0,7,7,0,4,1,0,1,4,9,6,5,6,9,4,1,0,1,4,9,5,3,3,5,9,4,1,0,1, %U A343720 4,9,4,1,0,1,4,9,4,1,0,1,4,9,3,12,10,10,12,3,9,4,1 %N A343720 Triangle read by rows: T(n,k) = k^2 mod n for k = 0..n-1, n >= 1. %C A343720 Similar to A048152 and A060036, but each row in this sequence begins at k = 0 and ends at k = n-1 (the minimum and maximum residues modulo n, respectively). %H A343720 Andrew Howroyd, <a href="/A343720/b343720.txt">Table of n, a(n) for n = 1..1275</a> (rows 1..50) %H A343720 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/QuadraticResidue.html">Quadratic Residue</a> %F A343720 T(n,k) = k^2 mod n. %F A343720 T(n,k) = T(n,n-k). %e A343720 Triangle begins: %e A343720 n\k| 0 1 2 3 4 5 6 7 8 9 10 11 %e A343720 ---+----------------------------------- %e A343720 1 | 0 %e A343720 2 | 0, 1 %e A343720 3 | 0, 1, 1 %e A343720 4 | 0, 1, 0, 1 %e A343720 5 | 0, 1, 4, 4, 1 %e A343720 6 | 0, 1, 4, 3, 4, 1 %e A343720 7 | 0, 1, 4, 2, 2, 4, 1 %e A343720 8 | 0, 1, 4, 1, 0, 1, 4, 1 %e A343720 9 | 0, 1, 4, 0, 7, 7, 0, 4, 1 %e A343720 10 | 0, 1, 4, 9, 6, 5, 6, 9, 4, 1 %e A343720 11 | 0, 1, 4, 9, 5, 3, 3, 5, 9, 4, 1 %e A343720 12 | 0, 1, 4, 9, 4, 1, 0, 1, 4, 9, 4, 1 %o A343720 (PARI) T(n,k) = k^2 % n \\ _Andrew Howroyd_, Jan 05 2024 %Y A343720 Cf. A048152, A060036. %K A343720 nonn,tabl %O A343720 1,13 %A A343720 _Jon E. Schoenfield_, Apr 26 2021