A034010 Number of 2n-step self avoiding closed walks on square grid, restricted to a quadrant and passing through origin.

0, 1, 2, 6, 20, 74, 300, 1302, 5944, 28266, 139010, 703102, 3641956, 19255106, 103630920, 566522778, 3140130354, 17620845976, 99977635264, 572935630884, 3313078283974

Offset: 1

Author

Felice Russo

Keywords

• nonn
• hard
• walk

Examples

			When the number of steps is 8, one of the six closed paths is
0___.
| ._|
|_|
		

Links

• B. Hayes, How to avoid yourself, American Scientist, Vol. 86, Number 4, Jul-August 1998. p. 314-319.

Crossrefs

A subset of the polyominoes with perimeter 2n (A006725), also a subset of A002931. Cf. A000105, A038373.

Extensions

Corrected and extended by David W. Wilson

a(16)-a(18) from Alex Chernov, Jan 22 2012

a(19)-a(21) from Bert Dobbelaere, Jan 06 2019