A203935 Number of lattice 2n-gons with edges on distinct lines.

1, 4, 26, 240, 2918, 44424, 816730, 17652320

Offset

2,2

Comments

a(n) is the number of self-avoiding polygons on the n X n square lattice having 2n edges (arbitrary perimeter) with an edge on each of the n distinct horizontal and n distinct vertical lines in the lattice.

Links

Table of n, a(n) for n=2..9.

StackExchange, Number of cycles in a grid such that each cycle traverse all the lines

Example

a(4)=26: 4 symmetries of the Z pentomino; 4 rotations of the step (123 bargraph) hexomino; 8 symmetries of each of the 132 and 213 bargraph hexominoes; and 2 rotations of the heptomino that consists of a 3x3 square with opposite corner cells removed.

Crossrefs

Sequence in context: A115416 A302606 A052577 * A210912 A210913 A210914

Adjacent sequences: A203932 A203933 A203934 * A203936 A203937 A203938

Keyword

nonn,more

Author

David Bevan, Jan 08 2012

Extensions

a(8) and a(9) from Francisco Mota, Jun 06 2013

Status

approved