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A057417
Number of staircase polygons of area n with any number of (staircase polygon) holes on square lattice (not allowing rotations).
1
1, 2, 4, 9, 20, 46, 105, 243, 561, 1303, 3026, 7047, 16419, 38314, 89454, 209056, 488810, 1143686, 2677074, 6269438, 14687799, 34423317, 80702234, 189258382, 443958607, 1041704375, 2444830929, 5739200960, 13475465449
OFFSET
1,2
LINKS
I. Jensen, Table of n, a(n) for n = 1..76 (from link below)
I. Jensen, More terms
CROSSREFS
Sequence in context: A036617 A367713 A007902 * A191653 A191827 A000968
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Aug 30 2000
STATUS
approved