A216874 Number of 2-cycle free city-block distance 1 permutations of a side-n hexagonal array.

0, 12, 19920, 6812201568, 298259688517544784

Offset

1,2

Links

Table of n, a(n) for n=1..5.

Example

Some solutions for n=3 (movement: 0=nw 1=ne 2=e 3=se 4=sw 5=w)
......3.5.5..........3.5.5..........2.4.3..........2.4.3..........3.5.5
.....4.3.1.5........4.3.1.5........1.5.1.3........4.0.1.5........4.5.1.5
....2.0.2.3.0......2.0.4.1.5......2.2.1.4.4......3.0.5.2.4......3.2.2.3.0
.....2.4.4.1........3.5.3.1........0.4.3.0........3.1.3.0........3.0.4.1
......0.2.0..........2.1.1..........0.0.5..........1.1.5..........1.2.0

Crossrefs

Sequence in context: A159421 A159369 A175882 * A012736 A013750 A127395

Adjacent sequences: A216871 A216872 A216873 * A216875 A216876 A216877

Keyword

nonn,hard,more

Author

R. H. Hardin Sep 18 2012

Status

approved