|
|
A123769
|
|
Number of ways to build a contiguous building with n LEGO blocks of size 1 X 2 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.
|
|
0
|
|
|
1, 2, 3, 6, 11, 23, 43, 93, 181, 392, 783, 1710, 3467, 7623, 15655, 34543, 71688, 158721, 332006, 737213, 1552365, 3455004, 7315948, 16315297, 34711474, 77544359, 165653643, 370623055
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
The base block is not counted among the n and must be the only block in the bottom layer of the building.
|
|
LINKS
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|