A210989 Number of one-sided polyominoes with 2n-1 cells.
1, 2, 18, 196, 2500, 33896, 476270, 6849777, 100203194, 1485200848, 22245940545, 336093325058, 5114451441106, 78306011677182, 1205243866707468, 18635412907198670, 289296535756895985, 4506983054619138245, 70436637624668665265
Offset: 1