A006782 Number of polygons of length 4n on L-lattice.

1, 0, 1, 2, 9, 36, 154, 684, 3128, 14666, 70258, 342766, 1698625, 8532410, 43368153, 222729492, 1154455161, 6033034032, 31760434883, 168311948410, 897327111964, 4810159375532, 25914118276362

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• more

References

• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Thorsten Ehlers, (C) simple generation algorithm
• I. G. Enting and A. J. Guttmann, Self-avoiding polygons on the square, L and Manhattan lattices, J. Phys. A 18 (1985), 1007-1017.
• Sean A. Irvine, Java program (github)

Crossrefs

Cf. A002931, A006781.

Extensions

a(13)-a(15) from Sean A. Irvine, Aug 01 2017

a(16)-a(21) from Thorsten Ehlers, Sep 30 2018

a(22) from Thorsten Ehlers, Nov 01 2018

a(23) from Thorsten Ehlers, Apr 16 2019