Eisenstein-Fibonacci sequences
Jonathan Post
jvospost3 at gmail.com
Sun Oct 22 22:58:41 CEST 2006
Eisenstein-Fibonacci sequences. Cube root of unity
analogues of square-root of unity A014291 Imaginary
Rabbits.
Let b(0) = w, b(1) = w^2, b(n) = w*b(n-1) + b(n-2),
where w = omega = (-1 + i*sqrt(3))/2 and w^2 = omega^2
= (-1 - i*sqrt(3))/2.
There are various integer sequences derived from this
complex sequence (such as the real part, the imaginary
part, the polynomial coefficient is of 1, w, and
w^2)Unless my arithmetic by hand is in error again,
is:
n b(n)
0 w
1 w^2
2 w(w^2) + w = w^3 + w = 1 + w.
3 w(1 + w) + w^2 = w + w^2 + w^2 = 1 + 2w^2.
4 w(1 + 2w^2) + 1 + w = w + 2w^3 + 1 + w = 3 + 2w.
5 w(3 + 2w) + 1 + 2w^2 = 3w + 2w^2 + 1 + 2w^2.
= 1 + 3w + 4w^2.
6 w(1 + 3w + 4w^2) + 3 + 2w = w + 3w^2 + 4w^3 + 3 +
2w
= 7 + 3w + 3w^2.
7 w(7 + 3w + 3w^2) + 1 + 3w + 4w^2 = 7w + 3w^2 + 3w^3
+ 1 + 3w + 4w^2 = 4 + 10w + 7w^2.
8 w(4 + 10w + 7w^2) + 7 + 3w + 3w^2 = 4w + 10w^2 +
7w^3 + 7 + 3w + 3w^2 = 14 + 7w + 13w^2.
9 w(14 + 7w + 13w^2) + 4 + 10w + 7w^2 = 14w + 7w^2 +
13w^3 + 4 + 10w + 7w^2 = 17 + 24w + 14w^2.
10 w(17 + 24w + 14w^2) + 14 + 7w + 13w^2 = 17w + 24w^2
+ 14w^3 + 14 + 7w + 13w^2 = 28 + 24w + 37w^2.
11 w(28 + 24w + 37w^2) + 17 + 24w + 14w^2 = 28w +
24w^2 + 37w^3 + 17 + 24w + 14w^2 = 54 + 52w +
38w^2.
12 w(54 + 52w + 38w^2) + 28 + 24w + 37w^2 = 54w +
52w^2 + 38w^3 + 28 + 24w + 37w^2 = 66 + 78w +
89w^2.
13 w(66 + 78w + 89w^2) + 54 + 52w + 38w^2 =
66w + 78w^2 + 89w^3 + 54 + 52w + 38w^2 =
143 + 118w + 116w^2.
14 w(143 + 118w + 116w^2) + 66 + 78w + 89w^2 =
143w + 118w^2 + 116w^3 + 66 + 78w + 89w^2 =
182 + 221w + 207w^2.
15 w(182 + 221w + 207w^2) + 143 + 118w + 116w^2 =
182w + 221w^2 + 207w^3 + 143 + 118w + 116w^2 =
350 + 300w + 337w^2.
The coefficients of 1 = a(n) = 0, 0, 1, 1, 3, 1, 7, 4,
14, 17, 28, 54, 66, 143, 182, 350, ...
which does not seem to be in OEIS.
To excerpt my comment in A107890 (and some other
seqs):
"Eisenstein integers are of the form a + b*omega,
where a and b are ordinary integers, and omega = (-1 +
i*sqrt(3))/2 is a cube root of 1, the other cube roots
of 1 being 1 and omega^2 = (-1 - i*sqrt(3))/2.
Eisenstein integers are complex numbers that are also
members of the imaginary quadratic field Q(sqrt -3) =
Z[omega]. The sums, differences, and products of
Eisenstein integers are other Eisenstein integers."
Other sequences come from:
b(0) = w, b(1) = w^2, b(n) = b(n-1) + w*b(n-2),
and from the O, J notation of Dörrie (1965) in
Weisstein, Eric W. "Eisenstein Integer." From
MathWorld--A Wolfram Web Resource.
http://mathworld.wolfram.com/EisensteinInteger.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.seqfan.eu/pipermail/seqfan/attachments/20061022/37a563e5/attachment-0001.htm>
More information about the SeqFan
mailing list