OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
Wikipedia, Pentomino
Index entries for linear recurrences with constant coefficients, signature (0,2,2,8,4,21,-8,-4,-6,0,-16,-8).
FORMULA
G.f.: -(4*x^6+x^3-1) / (8*x^12 +16*x^11 +6*x^9 +4*x^8 +8*x^7 -21*x^6 -4*x^5 -8*x^4 -2*x^3 -2*x^2+1).
a(n) mod 2 = A079978(n).
EXAMPLE
a(2) = 2, a(3) = 1:
.___. .___. ._____.
| | | | | ._. |
| ._| |_. | |_| |_|
|_| | | |_| |_ _|
| | | | | |_| |
|___| |___| |_____| .
MAPLE
a:= n-> (Matrix(12, (i, j)-> `if`(i+1=j, 1, `if`(i=12,
[-8, -16, 0, -6, -4, -8, 21, 4, 8, 2, 2, 0][j], 0)))^n.
<<1, 0, 2, 1, 12, 10, 59, 52, 276, 349, 1404, 1984>>)[1, 1]:
seq(a(n), n=0..35);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Nov 18 2016
STATUS
approved