20040214, 12:27  #1 
Feb 2004
23 Posts 
A Proposal for searching Recurrence Series Primes
Hi to everyone,
I am interested in searching the general properties of recurrence series, generally u(1)=p u(2)=q u(n+1)=u(n) + u(n1) where p and q are either 1 or prime. Famous examples of them are Fibonacci and Lucas numbers. We already know that there is no proof of finiteness of these numbers being prime. For now Fibonacci primality has been tested above n=400,000 already. I am both interested in relation degree higher than 3. The problem can be generalised as a function of f(p1,p2,...,pk,k) where k initial elements are stated and recurrence is developed as follows u(n+1) = SUM( u(n), u(n1), ... , u(n+1k) ) For the moment, my first challenge is to observe the behaviour of Fibonaccilike series with starting elements being changed. I am trying to construct frequency tables for prime numbers among the series, and extract relations between series in terms of primality and factors. What i have as a problem is the increasing # of digits and my insufficient programming skills. Also i may be short of information about this subject. Is there anyone that can help or advise some further thoughts for this proposal. Or any known programs that can be used/modified easily to use in this search. My questions may be a little confusing, if somebody is interested, all questions/criticisms are welcome! Bye 
20040422, 15:55  #2 
Bronze Medalist
Jan 2004
Mumbai,India
2^{2}×3^{3}×19 Posts 
Tribonacci/Tetranacci series and so on.

20040422, 16:40  #3 
Bronze Medalist
Jan 2004
Mumbai,India
100000000100_{2} Posts 
Tribonacci/tetranacc series and so on
Do you mean the tribonacci numbers 1,1,2,4,7,13,24,44,81...(summing of 3 terms) and related series like Lucas series?
It has been shown that the ratio between adjacent numbers as the sequence grows converges on 0.5436890125... the root of the cubic x^3+x^2 +x1=0 This series can be generalised by summing four terms (tetranacci numbers), five terms, 6 terms and so on. In all such sequences the ratio of adjacent terms converges to a limit. As the number of terms to be summed increases the limiting ratio gets smaller approaching 0.5 as a limit. In a generalised Fibonacci sequence if the first two no.s are divisible by a prime then all its no.s are divisible by the same prime. This sequence will contain a finite no. of primes. If the first two nos. are co prime (have no common diviser) the generalised sequence can contain no primes. There are infinitely many such sequences but the one with the smallest two starting no.s starts with 34 digit no.s! Mally. 
20040514, 09:26  #4 
Feb 2004
23_{10} Posts 
Thanks Mally, I appreciate for these infos.

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