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.
f(n) = sumdiv(n, d, n % (sum(m=0, n-1, Mod(m, n)^d == m)/sum(m=0, n-1, -Mod(m, n)^d == m)) == 0); \\ A337454 isok(n) = f(n) == 1;
f(n) = sumdiv(n, d, n % (sum(m=0, n-1, Mod(m, n)^d == m)/sum(m=0, n-1, -Mod(m, n)^d == m)) == 0); \\ A337454 isok(n) = f(n) == numdiv(n);
Triangle T(n,k) begins: n\k| 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ---+------------------------------------------------------ 1 | 1; 2 | 1, 1; 3 | 1, 3, 1; 4 | 1, 2, 1, 3; 5 | 1, 5, 1, 1, 1; 6 | 1, 3, 1, 3, 1, 3; 7 | 1, 7, 1, 3, 1, 3, 1; 8 | 1, 4, 1, 5, 1, 5, 1, 5; 9 | 1, 9, 1, 3, 1, 3, 1, 7, 1; 10 | 1, 5, 1, 1, 1, 5, 1, 1, 1, 5; 11 | 1, 11, 1, 3, 1, 3, 1, 3, 1, 3, 1; 12 | 1, 6, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9; 13 | 1, 13, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1; 14 | 1, 7, 1, 3, 1, 3, 1, 7, 1, 3, 1, 3, 1, 7; 15 | 1, 15, 1, 3, 1, 15, 1, 3, 1, 15, 1, 3, 1, 15, 1; 16 | 1, 8, 1, 5, 1, 9, 1, 5, 1, 9, 1, 5, 1, 9, 1, 5; 17 | 1, 17, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1; ... For (n, k) = (7, 3), there are three nonnegative values of m < n such that m^3 == m (mod 7) (namely 0, 1, and 6) and one nonnegative value of m < n such that -m^3 == m (mod 7) (namely 0), so T(7,3) = 3/1 = 3.
[[#[m: m in [0..n-1] | m^k mod n eq m]/#[m: m in [0..n-1] | -m^k mod n eq m]: k in [0..n-1]]: n in [1..17]];
T(n, k) = sum(m=0, n-1, Mod(m, n)^k == m)/sum(m=0, n-1, -Mod(m, n)^k == m); matrix(7, 7, n, k, k--; if (k>=n, 0, T(n,k))) \\ to see the triangle \\ Michel Marcus, Apr 17 2020
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