A056638 - OEIS

%I #6 Mar 30 2012 16:48:51

%S 2,122,3400,64210,959742,12294090,141329502,1500596864,14998956452,

%T 143004562082,1312929589140,11688960621918,101451353794222,

%U 861927965928610,7191518458613614,59078731187602024

%N Number of polygons of length 2n with two (self-avoiding polygon) holes on square lattice (not allowing rotations).

%H I. Jensen, <a href="/A056638/b056638.txt">Table of n, a(n) for n = 12..43</a> (from link below)

%H I. Jensen, <a href="http://www.ms.unimelb.edu.au/~iwan/polygons/series/square.perim.2hole.ser">More terms</a>

%Y Cf. A002931.

%K nonn

%O 12,1

%A _N. J. A. Sloane_, Aug 30 2000