|
|
A274663
|
|
Sum of n-th powers of the roots of x^3 + 4*x^2 - 11*x - 1.
|
|
4
|
|
|
3, -4, 38, -193, 1186, -6829, 40169, -234609, 1373466, -8034394, 47011093, -275049240, 1609284589, -9415668903, 55089756851, -322322100748, 1885860059450, -11033893589177, 64557712909910, -377717821061137, 2209972232664381, -12930227249420121
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,1
|
|
COMMENTS
|
This is half of a two sided sequences.
a(n) is x1^n + x2^n + x3^n, where x1, x2, x3 are the roots of the polynomial x^3 + 4*x^2 - 11*x - 1.
x1 = (cos(Pi/7))^2/(cos(2*Pi/7)*cos(4*Pi/7)),
x2 = -(cos(2*Pi/7))^2/(cos(4*Pi/7)*cos(Pi/7)),
x3 = -(cos(4*Pi/7))^2/(cos(Pi/7) *cos(2*Pi/7)).
|
|
LINKS
|
|
|
FORMULA
|
a(n) = ((cos(Pi/7))^2/(cos(2*Pi/7)*cos(4*Pi/7)))^n + (-(cos(2*Pi/7))^2/(cos(4*Pi/7)*cos(Pi/7)))^n + (-(cos(4*Pi/7))^2/(cos(Pi/7)*cos(2*Pi/7)))^n.
a(n) = -4*a(n-1) + 11*a(n-2) + a(n-3) for n>2.
a(n) = (-1/8)^(-n)*cos(Pi/7)^(3*n) + (-8)^n*sin(Pi/14)^(3*n) +
|
|
MATHEMATICA
|
RecurrenceTable[{a[0] == 3, a[1] == -4, a[2] == 38, a[n] == -4 a[n - 1] + 11 a[n - 2] + a[n - 3]}, a, {n, 0, 20}] (* Michael De Vlieger, Jul 02 2016 *)
LinearRecurrence[{-4, 11, 1}, {3, -4, 38}, 30] (* Harvey P. Dale, Dec 28 2022 *)
|
|
PROG
|
(PARI) polsym(x^3 + 4*x^2 - 11*x - 1, 21)
(PARI) Vec((3+8*x-11*x^2)/(1+4*x-11*x^2-x^3) + O(x^99)) \\ Altug Alkan, Jul 08 2016
|
|
CROSSREFS
|
|
|
KEYWORD
|
sign,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|