OFFSET
0,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,0,0,8).
FORMULA
a(n) = a(n-1) + 8*a(n-4).
a(n) = Sum_{k=0..n} binomial(n-k, floor(k/3)) * 2^k.
MATHEMATICA
CoefficientList[Series[(1+2x+4x^2)/(1-x-8x^4), {x, 0, 40}], x] (* or *) LinearRecurrence[{1, 0, 0, 8}, {1, 3, 7, 7}, 40] (* Harvey P. Dale, Feb 04 2015 *)
PROG
(PARI) x='x+O('x^30); Vec((1+2*x+4*x^2)/(1-x-8*x^4)) \\ G. C. Greubel, Feb 03 2018
(Magma) I:=[1, 3, 7, 7]; [n le 4 select I[n] else Self(n-1) + 8*Self(n-4): n in [1..30]]; // G. C. Greubel, Feb 03 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 16 2004
STATUS
approved