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Number of staircase polygons of perimeter 2n with 2 (staircase polygon) holes on square lattice (not allowing rotations).
1

%I #6 Mar 30 2012 16:48:52

%S 2,54,737,7330,60362,438284,2908069,18032906,106088843,598428100,

%T 3261717223,17278076588,89351738840,452686823796,2253216812878,

%U 11043624323310,53399946187312,255135202590382,1206067676613670

%N Number of staircase polygons of perimeter 2n with 2 (staircase polygon) holes on square lattice (not allowing rotations).

%H I. Jensen, <a href="/A057411/b057411.txt">Table of n, a(n) for n = 12..75</a> (from link below)

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

%K nonn

%O 12,1

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