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 A292076 #25 Jun 12 2025 10:17:09
%S A292076 0,192,5952,137664,2907456,59398080,1197999936,24040445376,
%T A292076 481452900672,9634211218368,192725453785920,3854838922404288,
%U A292076 77099417255585088,1542009455673733056,30840357998277021504,616808511044877643200,12336181029535005559104,246723707059807997713344
%N A292076 Number of 4-cycles in the n-Menger sponge graph.
%H A292076 Andrew Howroyd, <a href="/A292076/b292076.txt">Table of n, a(n) for n = 1..200</a>
%H A292076 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GraphCycle.html">Graph Cycle</a>.
%H A292076 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MengerSpongeGraph.html">Menger Sponge Graph</a>.
%H A292076 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (31,-244,480).
%F A292076 From _Andrew Howroyd_, Jun 12 2025: (Start)
%F A292076 a(n) = Sum_{k=1..n-1} 8*3^(k-1)*A291066(n-k).
%F A292076 a(n) = 16*(5*20^n - 17*8^n + 12*3^n)/85. (End)
%o A292076 (PARI) a(n) = 16*(5*20^n - 17*8^n + 12*3^n)/85 \\ _Andrew Howroyd_, Jun 12 2025
%Y A292076 Cf. A291066 (edges), A292075 (6-cycles).
%K A292076 nonn,easy
%O A292076 1,2
%A A292076 _Eric W. Weisstein_, Sep 12 2017
%E A292076 a(7) onwards from _Andrew Howroyd_, Jun 12 2025