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 A222204 Write n=3i+j, 0<=j<3; a(n) = number of ways to cover the r X s grid graph by vertex disjoint cycles, where (r,s) = (2i+2, 2i+2) (if j=0), (2i+2, 2i+3) (if j=1) or (2i+3, 2i+4) (if j=2). 2

%I #9 Jan 01 2019 06:52:42

%S 1,1,3,18,54,1140,13903,99051,13049563,360783593,6044482889,

%T 4738211572702,303872744726644,11986520595161863,54755153078468134960,

%U 8217125138015950451626,764291947227525464744293,20119942924108379011391597989,7095967027221343377167292602835,1558052539448513320447263528275071

%N Write n=3i+j, 0<=j<3; a(n) = number of ways to cover the r X s grid graph by vertex disjoint cycles, where (r,s) = (2i+2, 2i+2) (if j=0), (2i+2, 2i+3) (if j=1) or (2i+3, 2i+4) (if j=2).

%C An interleaving of A222202 and A222203.

%H Peter Tittmann, <a href="http://www.htwm.de/~peter/research/enumeration.html">Enumeration in graphs: counting Hamiltonian cycles</a> [Broken link?]

%H Peter Tittmann, <a href="http://web.archive.org/web/20101127064650/https://www.staff.hs-mittweida.de/~peter/research/enumeration.html">Enumeration in graphs: counting Hamiltonian cycles</a> [Backup copy of top page only, on the Internet Archive]

%Y Cf. A222202, A222203.

%K nonn

%O 0,3

%A _N. J. A. Sloane_, Feb 14 2013

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Last modified May 29 15:14 EDT 2023. Contains 363042 sequences. (Running on oeis4.)