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 A298198 #17 Feb 16 2025 08:33:53 %S A298198 4,40,320,2368,16832,116608,793088,5318656,35271680,231786496, %T A298198 1511653376,9795518464,63126683648,404881506304,2586017398784, %U A298198 16456474427392,104381066510336,660139718213632,4163958223142912,26202468819927040,164527129801785344 %N A298198 Number of Eulerian cycles in the graph Cartesian product of C_n and a double edge. %C A298198 When n = 2 the graph is the Cartesian product of two double edges. %C A298198 a(n) is divisible by 2^(n + 1). %H A298198 Andrew Howroyd, <a href="/A298198/b298198.txt">Table of n, a(n) for n = 1..500</a> %H A298198 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/EulerianCycle.html">Eulerian Cycle</a> %H A298198 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (14, -60, 72). %F A298198 a(n) = 14*a(n-1) - 60*a(n-2) + 72*a(n-3) for n > 3. %F A298198 G.f.: 4*x*(1 - 4*x)/((1 - 2*x)*(1 - 6*x)^2). %o A298198 (PARI) Vec(4*(1 - 4*x)/((1 - 2*x)*(1 - 6*x)^2) + O(x^30)) %Y A298198 Row 2 of A298117. %K A298198 nonn %O A298198 1,1 %A A298198 _Andrew Howroyd_, Jan 14 2018