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A227959 Number of tilings using monominoes and L-triominoes in 2 x n chessboard, such that three monominoes cannot occur together in shape of L-triomino. 1
1, 1, 4, 6, 20, 38, 104, 220, 556, 1244, 3024, 6944, 16576, 38536, 91216, 213280, 502864, 1178928, 2774592, 6512864, 15315072, 35969952, 84550912, 198634048, 466825152, 1096838208, 2577550336, 6056474880, 14232064256, 33441977216, 78583660288, 184655188480 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

A problem from <a href="https://brilliant.org/i/AQs2Zw/">brilliant.org</a>

LINKS

Gopinath A. R., Table of n, a(n) for n = 0..200

Index entries for linear recurrences with constant coefficients, signature (0,4,2,2,4).

FORMULA

a(n) = 4*a(n-2) + 2*a(n-3) + 2*a(n-4) + 4*a(n-5), with a(0)=1, a(1)=1, a(2)=4, a(3)=6, and a(4)=20.

G.f.: (1+x)/(1-4*x^2-2*x^3-2*x^4-4*x^5).

Asymptotic formula: a(n) ~ 0.581189405182598 * 2.3498153157195^n.

PROG

(Sage)

fx = (1+x)/(1-4*x^2-2*x^3-2*x^4-4*x^5)

fxt = taylor(fx, x, 0, 50)

for i in xrange(51):

....print i, fxt.coefficient(x, i)

(PARI) Vec( (1+x)/(1-4*x^2-2*x^3-2*x^4-4*x^5) +O(x^66) ) \\ Joerg Arndt, Aug 07 2013

CROSSREFS

Cf. A127864.

Sequence in context: A273995 A026788 A079435 * A088015 A027377 A048789

Adjacent sequences:  A227956 A227957 A227958 * A227960 A227961 A227962

KEYWORD

nonn,easy

AUTHOR

Gopinath A. R., Aug 01 2013

STATUS

approved

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Last modified September 26 15:27 EDT 2017. Contains 292531 sequences.