OFFSET
0,3
REFERENCES
G. Kreweras, Recouvrements d'un rectangle de largeur 3 à l'aide de triminos, Mathématiques et sciences humaines, tome 130 (1995), p. 27-31.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
Wikipedia, Tromino
Index entries for linear recurrences with constant coefficients, signature (1,2,6,1,0,-1).
FORMULA
a(n) = a(n-1) +2*a(n-2) +6*a(n-3) +a(n-4) -a(n-6).
G.f.: (1-x^3) / (1-x-2*x^2-6*x^3-x^4+x^6). - Alois P. Heinz, Oct 09 2008
MAPLE
a:= n-> (Matrix([[1$2, 0$2, 1, 0]]). Matrix(6, (i, j)-> if i+1=j then 1 elif j=1 then [1, 2, 6, 1, 0, -1][i] else 0 fi)^n)[1, 2]: seq(a(n), n=0..30); # Alois P. Heinz, Oct 09 2008
MATHEMATICA
LinearRecurrence[{1, 2, 6, 1, 0, -1}, {1, 1, 3, 10, 23, 62}, 40] (* Harvey P. Dale, Aug 27 2013 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Philippe Deléham, Jan 18 2008
EXTENSIONS
More terms from Alois P. Heinz, Oct 09 2008
STATUS
approved