|
|
A221909
|
|
a(n) = 7^n + 7*n.
|
|
4
|
|
|
1, 14, 63, 364, 2429, 16842, 117691, 823592, 5764857, 40353670, 282475319, 1977326820, 13841287285, 96889010498, 678223072947, 4747561510048, 33232930569713, 232630513987326, 1628413597910575
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
LINKS
|
|
|
FORMULA
|
G.f.: (1+5*x-48*x^2)/((1-x)^2*(1-7*x)).
a(n) = 9*a(n-1)-15*a(n-2)+7*a(n-3).
|
|
MATHEMATICA
|
Table[(7^n + 7 n), {n, 0, 30}] (* or *) CoefficientList[Series[(1 + 5 x - 48 x^2)/((1 - x)^2 (1 - 7 x)), {x, 0, 30}], x]
|
|
PROG
|
(Magma) [7^n + 7*n: n in [0..30]]; /* or */ I:=[1, 14, 63]; [n le 3 select I[n] else 9*Self(n-1)-15*Self(n-2)+7*Self(n-3): n in [1..30]];
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|