Permutation Of Some Primes
Leroy Quet
qq-quet at mindspring.com
Fri Apr 2 20:27:03 CEST 2004
I wrote in part:
>If you take the first n primes, you can (for some n) find a permutation
>of them such that the greatest prime divisors of each sum of consecutive
>primes (consecutive in regards to their placement in the permutation)
>forms a permutation of the first (n-1) primes
>(so that each greatest prime-divisor q, q <= the (n-1)th prime, occurs
>once exactly).
>
>For example, with n = 4, we have:
>
>primes in their permutation:
>2, 7, 3, 5
>
>sums of consecutive primes:
>9, 10, 8
>
>greatest prime divisors:
>3, 5, 2
>
>
>...
>
>And more generally, what is the sequence which gives how many such
>permutations like this are there for the first n primes?
>
>thanks,
>Leroy Quet
Another sequence idea based on the above:
Let a(1) = 2;
Let a(m+1), m >= 1, be the lowest prime not among the first m terms of
the sequence where
the highest prime divisor, b(m), of (a(m)+a(m+1)) is not among the first
(m-1) b's.
So we have 3 sequences:
a(m): 2, 3, 5, 7, 19, 23, 11, 47, 29,...
a(m)+a(m+1): 5, 8, 12, 26, 42, 34, 58, 76,..
b(m): 5, 2, 3, 13, 7, 17, 29, 19 ,..
(if I did not err.)
I wonder most, in regards to these sequences, are {a(m)} and {b(m)}
permutations of the primes?
thanks,
Leroy Quet
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