A006782 Number of polygons of length 4n on L-lattice. (Formerly M1930)

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

Offset

1,4

References

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

Links

Table of n, a(n) for n=1..23.

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.

Sequence in context: A150967 A344108 A121769 * A150968 A073156 A150969

Adjacent sequences: A006779 A006780 A006781 * A006783 A006784 A006785

Keyword

nonn,more

Author

N. J. A. Sloane

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

Status

approved