Permutations, Fractions, Primes
Leroy Quet
qq-quet at mindspring.com
Sat Dec 23 17:54:21 CET 2006
Joseph Biberstine wrote:
>Naive Mathematica one-liner:
>Table[Max[Map[Length[Select[#, PrimeQ[#] &]] &, Map[Join[Numerator /@ #,
>Denominator /@ #] &, Map[Table[Sum[1/#[[k]], {k, 1, m}], {m, 1,
>Length[#]}] &, Permutations[Range[n]]]]]], {n, 1, 9}]
>
>Sequences begins (from n=1):
>{0, 3, 4, 4, 6, 8, 8, 10, 11}
>
>OEIS absent already.
>
>A naive maximum: 2n :)
>
>-JRB
>
>Leroy Quet wrote (in part):
>> First, take a permutation {b(k)} of the first n positive integers, and
>> then take the partial sums,...
>....
>> If we make a game of this, a better player might play the permutation
>> (2,6,1,4,5,3),
>>
>> which gives the s(m)'s
>> 1/2, 2/3, 5/3, 23/12, 127/60, 49/20.
>>
>>
>> So we have the primes: 2,2,3,5,3,23,127, for a score of 7.
>>
>> My question is, what is the maximum possible score for each given n?
>>
>> I get the sequence beginning
>> 0,3,4,4,...
I see that Joseph Biberstine has computed an 8 for the 6th term.
So I was encouraged to find an n=6 permutation that gives a score of 8.
(Luckily, I found a permutation relatively quickly.)
2,6,1,3,5,4
The s(m)'s:
1/2,2/3,5/3,2/1,11/5,49/20.
(Yay!)
I would ask someone to compute more terms so this sequence can be
submitted to the EIS, but, as is the case wih many game-derived
sequences, the relatively long explanation of the sequence may make it
too esoteric to be interesting to a general audience.
Thanks,
Leroy Quet
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