|
| |
|
|
A152119
|
|
a(n) = prod(k=1..(n-1)/2, 5 + 4*cos(k*Pi/n)^2 ).
|
|
1
|
|
|
|
1, 1, 1, 6, 7, 41, 48, 281, 329, 1926, 2255, 13201, 15456, 90481, 105937, 620166, 726103, 4250681, 4976784, 29134601, 34111385, 199691526, 233802911, 1368706081, 1602508992, 9381251041, 10983760033, 64300051206, 75283811239
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
0,4
|
|
|
LINKS
|
Table of n, a(n) for n=0..28.
|
|
|
FORMULA
|
a(n) = prod(k=1..(n-1)/2, 5 + 4*cos(k*Pi/n)^2 ).
a(n) = +7*a(n-2) -1*a(n-4). G.f.: (x^4 - x^3 - 6*x^2 + x + 1)/((x^2 - 3*x + 1)*(x^2 + 3*x + 1)). [Joerg Arndt, Jan 24 2013]
|
|
|
MATHEMATICA
|
a = Table[Product[5 + 4*Cos[k*Pi/n]^2, {k, 1, (n - 1)/2}], {n, 0, 10}]; FullSimplify[ExpandAll[a]]
Denominator[NestList[(5/(5+#))&, 0, 60]] (* Vladimir Joseph Stephan Orlovsky, Apr 13 2010 *)
|
|
|
CROSSREFS
|
Sequence in context: A027021 A013627 A219212 * A041080 A042091 A047181
Adjacent sequences: A152116 A152117 A152118 * A152120 A152121 A152122
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Roger L. Bagula and Gary W. Adamson, Nov 24 2008
|
|
|
STATUS
|
approved
|
| |
|
|
