OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,16).
FORMULA
a(n) = a(n-1) + 16*a(n-5).
a(n) = Sum_{k=0..n} binomial(n-k, floor(k/4)) * 2^k.
MATHEMATICA
CoefficientList[Series[(1+2*x+4*x^2+8*x^3)/(1-x-16*x^5), {x, 0, 50}], x] (* or *) LinearRecurrence[{1, 0, 0, 0, 16}, {1, 3, 7, 15, 15}, 50] (* G. C. Greubel, Feb 03 2018 *)
PROG
(PARI) x='x+O('x^30); Vec((1+2*x+4*x^2+8*x^3)/(1-x-16*x^5)) \\ G. C. Greubel, Feb 03 2018
(Magma) I:=[1, 3, 7, 15, 15]; [n le 5 select I[n] else Self(n-1) +16*Self(n-5): n in [1..30]]; // G. C. Greubel, Feb 03 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 16 2004
STATUS
approved