Previous: 5 Relations between lengths
Up: Patterns Occurring During the
Next: Bibliography
Definition 6.1
A pattern of length

where

, i.e.

will be referred as a "nothing but

"
pattern, and a pattern of length

where

will be referred as an "any, one, one" pattern (the
sequence

must be palindromic, since

has to be so).
Proposition 6.2
A "nothing but ones" is known to be a pattern of
second kind for all length

(from theorem
4.10).
When

, the corresponding

and

are given by:
 |
(6.1) |
where

. Additionally, the parameter

must be even when

.
Proof.
We have

, where

is the

-th Fibonacci number. Thus the signatures
are given by:
and criterion of corollary
4.11 is satisfied
(when

,

is also a pattern of
first kind and the parity condition over

is here to select
the

). The formulae
are straightforward. Finally,
6.1 is an
asymptotic formula, based upon
It can be checked that
6.1 holds from

,
while the empty pattern occurs when

.
Proposition 6.3
A "nothing but fours" pattern is a pattern of first
kind for all length

, and

can ever
be additionally required. In such a case, we have:
 |
(6.2) |
where

.
Proof.
We have

, where

is defined by

and

.
Thus the signatures are alternatively

and

and criterion
of theorem
4.10 (cor.
4.12)
is satisfied. Formulae
are straightforward and lead to

. Finally,
6.2
is an asymptotic formula, based upon
In fact,
6.2 holds from the beginning.
Remark 6.4
We have therefore proven that it exists an infinite number of quadratic
integers of each kind having a given period length. But the

and

found are quickly huge, and give no hint about the smallest

having a given period length.
Proposition 6.6
An "any, one, one" pattern is known from theorem
4.10 to be a pattern of second kind if and only
if its middle element is odd or none. In such a case, all the

associated to a

belong to the same pattern of first
kind

, where

. And we have
Conversely, if a pattern

where all

are even and at least

belongs to some

such that

is even, then all such

share also
the above described

as pattern of second kind.
Proof.
An "any, one, one" pattern is the product of one
matrix

and several matrices

where
The value of the

pattern follows from :
proving that

is a fixed point of

when

is a fixed point of

. Conversely, if

is a fixed point of

and

as described, then

is a pattern,

is odd and

is a fixed
point of

.
Definition 6.7
The alternate pattern

is defined by

when

and, otherwise, by

.
The pseudo period of

is the period associated to

,
i.e one or three (ordinary) periods of

.
If we plot the period of
versus the pseudo-period of
for all
in
, we obtain
FIG. 1.1 (left : the whole figure; right:
the lower left corner zoomed in).
FIG. 6.1:
Period of
versus the pseudo-period of
.
|
|
**
Previous: 5 Relations between lengths
Up: Patterns Occurring During the
Next: Bibliography
douillet@ensait.fr
2004-02-06