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 A373784 #10 Jul 19 2024 21:46:11
%S A373784 1,3,73,17083,36899281,723299706163,127954611219059353,
%T A373784 203907700711025670584683,2925406687944886208690683289761,
%U A373784 377768302929213133608351637048047649123,439058106335101098121200963942043393433721555433,4592676942963368381676178826582121303149079572759596838683
%N A373784 Number of n X n periodic matrices over GF(3).
%C A373784 T is a periodic matrix if T = T^k for some k > 1. T is periodic iff image(T) = image(T^2) iff x^2 does not divide the minimal polynomial of T.
%H A373784 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PeriodicMatrix.html">Periodic Matrix</a>
%F A373784 Sum_{n>=0}a_n*x^n/B(n) = e(x)*f(x) where B(n) = A053290(n)/2^n, e(x) = Sum{n>=0}x^n/B(n) and f(x) = Sum_{n>=0} (2x)^n.
%t A373784 nn = 11; B[n_] := Product[q^n - q^i, {i, 0, n - 1}]/(q - 1)^n /. q -> 3;
%t A373784 e[x_] := Sum[x^n/B[n], {n, 0, nn}];f[x_] := Sum[(q - 1)^n x^n, {n, 0, nn}] /. q -> 3; Table[B[n], {n, 0, nn}] CoefficientList[Series[e[x] f[ x], {x, 0, nn}], x]
%Y A373784 Cf. A348015, A053290.
%K A373784 nonn
%O A373784 0,2
%A A373784 _Geoffrey Critzer_, Jun 18 2024