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).

1, 1, 3, 18, 54, 1140, 13903, 99051, 13049563, 360783593, 6044482889, 4738211572702, 303872744726644, 11986520595161863, 54755153078468134960, 8217125138015950451626, 764291947227525464744293, 20119942924108379011391597989, 7095967027221343377167292602835, 1558052539448513320447263528275071

Offset

0,3

Comments

An interleaving of A222202 and A222203.

Links

Table of n, a(n) for n=0..19.

Peter Tittmann, Enumeration in graphs: counting Hamiltonian cycles [Broken link?]

Peter Tittmann, Enumeration in graphs: counting Hamiltonian cycles [Backup copy of top page only, on the Internet Archive]

Crossrefs

Cf. A222202, A222203.

Sequence in context: A361083 A027334 A130505 * A027289 A061317 A190313

Adjacent sequences: A222201 A222202 A222203 * A222205 A222206 A222207

Keyword

nonn

Author

N. J. A. Sloane, Feb 14 2013

Status

approved