OFFSET
0,3
COMMENTS
Here is the 3-row trapezoid of average length 6 (with 18 cells):
___ ___ ___ ___ ___
| | | | | |
_|___|___|___|___|_ _|_
| | | | | | |
_|___|___|___|___|_ _|___|_
| | | | | | | |
|___|___|___|___|___|___|___|,
and here are the two types of (triangular and rectangular) tiles of size 3, which can be rotated as needed:
___
| |
_|___|_ ___________
| | | | | | |
|___|___|, |___|___|___|.
As an example, here is one of the a(6) = 107 ways to tile the 3-row trapezoid
___ ___ ___________
| | | |
_| _|_ |___________|_
| | | | | |
_| _| |_ |_ _| |_
| | | | | |
|___|_______|___|___|_______|.
LINKS
Index entries for linear recurrences with constant coefficients, signature (2,0,4,-1,0,-1).
FORMULA
MATHEMATICA
LinearRecurrence[{2, 0, 4, -1, 0, -1}, {0, 1, 3, 6, 16, 43}, 40]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Greg Dresden and Mingjun Oliver Ouyang, Aug 30 2024
STATUS
approved