OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..5000
J. Hietarinta and C.-M. Viallet, Discrete Painlevé I and singularity confinement in projective space, Chaos, Solitons and Fractals 11, 2000, p. 29.
Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-2,1).
FORMULA
From G. C. Greubel, Mar 22 2023: (Start)
a(n) = (1/3)*(2*n^2 - n + 3 + 2*floor((n+2)/3) + floor((n+1)/3)).
MATHEMATICA
CoefficientList[Series[(1+x^2+2x^4)/((1-x^3)(1-x)^2), {x, 0, 70}], x] (* Harvey P. Dale, Mar 31 2011 *)
PROG
(PARI) Vec((1+x^2+2*x^4)/(1-x^3)/(1-x)^2+O(x^99)) \\ Charles R Greathouse IV, Sep 10 2014
(Magma) [(2*n^2 -n +3 +2*Floor((n+2)/3) +Floor((n+1)/3))/3: n in [0..60]]; // G. C. Greubel, Mar 22 2023
(SageMath) [(2*n^2 -n +3 +2*((n+2)//3) +((n+1)//3))/3 for n in range(61)] # G. C. Greubel, Mar 22 2023
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 16 2003
STATUS
approved