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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 November 14 19:55 EST 2019. Contains 329128 sequences. (Running on oeis4.)