Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1x2 which is flat, i.e. with all blocks in parallel position.
1, 2, 7, 24, 99, 416, 1854, 8407, 38970, 182742, 866442, 4140607, 19925401
1 seqfan posts
Thu Mar 29 03:07:03 CEST 2012 [seqfan] 2n-ominoes tiled by 1x2 rectangles