%I
%S 1,2,5,14,42,132,430,1442,4956,17400,62251,226506,836911,3136182,
%T 11906908,45761338,177903128,699167112,2776219871,11132523840,
%U 45062497156,184057276510,758328417263,3150593560374,13195743501195
%N Number of staircase polygons of perimeter 2n with any number of (staircase polygon) holes on square lattice (not allowing rotations).
%H I. Jensen, <a href="/A057413/b057413.txt">Table of n, a(n) for n = 2..51</a>
%H I. Jensen, <a href="http://www.ms.unimelb.edu.au/~iwan/polygons/series/staircase.perim.allholes.ser">More terms</a>
%K nonn
%O 2,2
%A _N. J. A. Sloane_, Aug 30 2000
