OFFSET
1,5
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,1,-1,3,1,1,-1).
FORMULA
Taking A099328 to A099331 as the rows of an array T, the recurrences for these row sequences are given for n>=2 by T(n, 0) = T(n-1, 2) + T(n-2, 1), T(n, 1) = T(n-1, 3) + T(n-2, 0) + T(n-2, 2), T(n, 2) = T(n-1, 0) + T(n-2, 1) + T(n-2, 3), T(n, 3) = T(n-1, 1) + T(n-2, 2), with initial values T(0, 0)=1, T(1, 2)=1.
From Chai Wah Wu, Aug 09 2016: (Start)
a(n) = a(n-1) + a(n-2) - a(n-3) + 3*a(n-4) + a(n-5) + a(n-6) - a(n-7) for n > 7.
G.f.: x*(1 - x - 2*x^4)/((x^4 - 2*x^3 - 1)*(x^3 + x^2 + x - 1)). (End)
EXAMPLE
a(6) counts 8 paths from (0,0) to (6,0); the final move in 5 of the paths is from the point (5,2) and the final move in the other 3 paths is from (4,1).
MATHEMATICA
LinearRecurrence[{1, 1, -1, 3, 1, 1, -1}, {1, 0, 1, 0, 2, 2, 8}, 40] (* Harvey P. Dale, Aug 11 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Oct 12 2004
STATUS
approved