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 A108498 #3 Mar 30 2012 18:51:39
%S A108498 0,0,0,0,2,0,0,2,0,0,0,2,3,4,0,0,0,0,0,0,0,0,2,3,4,5,6,0,0,6,0,4,0,2,
%T A108498 0,0,0,5,3,0,2,6,0,8,0,0,6,2,0,0,0,6,2,0,0,0,2,3,4,5,6,7,8,9,10,0,0,6,
%U A108498 0,0,0,6,0,0,0,6,0,0,0,2,3,4,5,6,7,8,9,10,11,12,0,0,6,12,6,2,0,0,0,6,12,6,2
%N A108498 Triangle read by rows: T(n,k) = sum_i{1<=i<=n} k^i mod n, showing 1<=k<=n.
%F A108498 T(n, k+n)=T(n, k). T(n, 0)=T(n, 1)=T(n, n)=T(1, k)=T(2, k)=T(6, k)=T(42, k)=T(1806, k)=0. T(p, k)=k for p prime and 1<k<p.
%e A108498 Rows start: 0; 0,0; 0,2,0; 0,2,0,0; 0,2,3,4,0; 0,0,0,0,0,0; 0,2,3,4,5,6,0; etc.
%e A108498 T(7,3) = 3+9+27+81+243+729+2187 mod 7 = 3279 mod 7 = 3.
%Y A108498 Cf. A014117, A059721, A108048, A108497, A108499.
%K A108498 nonn,tabl
%O A108498 1,5
%A A108498 _Henry Bottomley_, Jun 06 2005