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 A298198 Number of Eulerian cycles in the graph Cartesian product of C_n and a double edge. 2
 4, 40, 320, 2368, 16832, 116608, 793088, 5318656, 35271680, 231786496, 1511653376, 9795518464, 63126683648, 404881506304, 2586017398784, 16456474427392, 104381066510336, 660139718213632, 4163958223142912, 26202468819927040, 164527129801785344 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS When n = 2 the graph is the Cartesian product of two double edges. a(n) is divisible by 2^(n + 1). LINKS Andrew Howroyd, Table of n, a(n) for n = 1..500 Eric Weisstein's World of Mathematics, Eulerian Cycle FORMULA a(n) = 14*a(n-1) - 60*a(n-2) + 72*a(n-3) for n > 3. G.f.: 4*x*(1 - 4*x)/((1 - 2*x)*(1 - 6*x)^2). PROG (PARI) Vec(4*(1 - 4*x)/((1 - 2*x)*(1 - 6*x)^2) + O(x^30)) CROSSREFS Row 2 of A298117. Sequence in context: A061318 A277652 A190541 * A043031 A121126 A145730 Adjacent sequences: A298195 A298196 A298197 * A298199 A298200 A298201 KEYWORD nonn AUTHOR Andrew Howroyd, Jan 14 2018 STATUS approved

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Last modified March 24 04:28 EDT 2023. Contains 361454 sequences. (Running on oeis4.)