|
|
A089979
|
|
Expansion of 1/(1-4x-4x^3).
|
|
3
|
|
|
1, 4, 16, 68, 288, 1216, 5136, 21696, 91648, 387136, 1635328, 6907904, 29180160, 123261952, 520679424, 2199438336, 9290801152, 39245922304, 165781442560, 700288974848, 2958139588608, 12495684124672, 52783892398080
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
LINKS
|
|
|
FORMULA
|
a(n) = Sum_{k=0..floor(n/2)} C(n-2*k, k)*4^(n-2*k).
|
|
MATHEMATICA
|
CoefficientList[Series[1/(1 - 4*x - 4*x^3), {x, 0, 50}], x] (* or *) LinearRecurrence[{4, 0, 4}, {1, 4, 16}, 50] (* G. C. Greubel, Apr 29 2017 *)
|
|
PROG
|
(PARI) x='x+O('x^50); Vec(1/(1 - 4*x - 4*x^3)) \\ G. C. Greubel, Apr 29 2017
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|