[seqfan] Re: 8/5 Sequence
franktaw at netscape.net
franktaw at netscape.net
Wed Sep 30 13:51:47 CEST 2009
> Hi, Seqfan
>
> 8/5 Sequence :
>
> IF x=Even THEN x=x/2
> IF x=Odd AND
> 8*x=0 Mod 5 THEN x=(8*x+5)/5
> 8*x=1 Mod 5 THEN x=(8*x+4)/5
> 8*x=2 Mod 5 THEN x=(8*x+3)/5
> 8*x=3 Mod 5 THEN x=(8*x+2)/5
> 8*x=4 Mod 5 THEN x=(8*x+1)/5
This can be simplified: if x is odd, then next x is floor(8/5*x)+1.
>...
> It is easy to generalize the sequence.
>
> m/ n Sequence :
> IF x=Even THEN x=x/2
> IF x=Odd AND
> m*x=0 Mod n THEN x=(m*x+n)/n
> m*x=1 Mod n THEN x=(m*x+n-1)/n
> m*x=2 Mod n THEN x=(m*x+n-2)/n
> ………....
> m*x=n-1 Mod n THEN x=(m*x+1)/n
No need for separate m and n; let r be the ratio (m/n), and if x is
odd, the next x is floor(r*x)+1. And now we don't even need r to be
rational.
>...
When r is the golden ratio, (sqrt(5)+1)/2, starting with 3, we get
A001595, a sequence of all odd numbers, so there is unlimited growth.
This may shed some light on what is happening with 8/5.
(Is A128587 a signed version of A001595?
http://www.research.att.com/~njas/sequences/?q=id%3AA001595|id%3AA128587
)
Franklin T. Adam
s-Watters
More information about the SeqFan
mailing list