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Number of staircase polygons of perimeter 2n with one (staircase polygon) hole on square lattice (not allowing rotations).
4

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

%S 1,12,94,604,3463,18440,93274,454412,2151673,9964500,45335002,

%T 203303760,900901387,3952468348,17194102478,74257185512,318693463933,

%U 1360298775524,5778468266446,24442845038580

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

%H I. Jensen, <a href="/A057410/b057410.txt">Table of n, a(n) for n = 8..103</a> (from link below)

%H I. Jensen, <a href="http://www.ms.unimelb.edu.au/~iwan/polygons/series/staircase.perim.1hole.ser">More terms</a>

%K nonn

%O 8,2

%A _N. J. A. Sloane_, Aug 30 2000, corrected Aug 29 2006