A006782 - OEIS

%I M1930 #40 May 18 2019 07:23:19

%S 1,0,1,2,9,36,154,684,3128,14666,70258,342766,1698625,8532410,

%T 43368153,222729492,1154455161,6033034032,31760434883,168311948410,

%U 897327111964,4810159375532,25914118276362

%N Number of polygons of length 4n on L-lattice.

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

%H Thorsten Ehlers, <a href="/A006782/a006782_1.c.txt">(C) simple generation algorithm</a>

%H I. G. Enting and A. J. Guttmann, <a href="http://www.cmar.csiro.au/e-print/internal/enting_x1985e.pdf">Self-avoiding polygons on the square, L and Manhattan lattices</a>, J. Phys. A 18 (1985), 1007-1017.

%H Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a006/A006782.java">Java program</a> (github)

%Y Cf. A002931, A006781.

%K nonn,more

%O 1,4

%A _N. J. A. Sloane_

%E a(13)-a(15) from _Sean A. Irvine_, Aug 01 2017

%E a(16)-a(21) from _Thorsten Ehlers_, Sep 30 2018

%E a(22) from _Thorsten Ehlers_, Nov 01 2018

%E a(23) from _Thorsten Ehlers_, Apr 16 2019