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A253809 Array of pairs (x,y) of Markoff triples (x,y,z) with x <= y <= z, for z given in A002559. 0
1, 1, 1, 1, 1, 2, 1, 5, 2, 5, 1, 13, 1, 34, 2, 29, 5, 13, 1, 89, 5, 29, 1, 233, 2, 169, 13, 34, 1, 610, 5, 194, 1, 1597, 2, 985, 5, 433, 13, 194, 34, 89, 1, 4181, 29, 169, 1, 10946, 2, 5741, 29, 433, 5, 2897, 13, 1325, 89, 233, 1, 28657 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

Frobenius' conjecture on Markoff triples is that the maximal member z of the triple of positive integers (x,y,z), satisfying  x^2 + y^2 + z^2 - 3*x*y*z = 0, with x <= y <= z, determines x and y uniquely. Also, each entry from A002559 (Markoff numbers) is conjectured to appear as a maximal member z. If an entry A002559(n) should not appear as z then one puts z(n) = 0 and row n will be 0, 0.

If this Frobenius conjecture is true then the row length of this array is always 2, and only positive numbers appear.

REFERENCES

R. A. Mollin, Advanced Number Theory with Applications, Chapman & Hall/CRC, Boca Raton, 2010, 123-125.

See also A002559.

LINKS

Table of n, a(n) for n=1..60.

Feng-Juan Chen and Yong-Gao Chen, On the Frobenius conjecture for Markoff numbers, J. Number Theory 133 (2013) 2363-2373.

Don Zagier, On the number of Markoff numbers below a given bound, Mathematics of Computation 39:160 (1982), pp. 709-723.

See also A002559.

EXAMPLE

The array A(n,k) begins:

If the Frobenius conjecture is true there will only be one pair x(1,n), y(1,n) for each z(n).

n     z(n) \  k=1: x(1,n)  k=2: y(1,n) ...

1       1:      1            1

2       2:      1            1

3       5:      1            2

4      13:      1            5

5      29:      2            5

6      34:      1           13

7      89:      1           34

8     169:      2           29

9     194:      5           13

10    233:      1           89

11    433:      5           29

12    610:      1          233

13    985:      2          169

14   1325:     13           34

15   1597:      1          610

16   2897:      5          194

17   4181:      1         1597

18   5741:      2          985

19   6466:      5          433

20   7561:     13          194

21   9077:     34           89

22  10946:      1         4181

23  14701:     29          169

24  28657:      1        10946

25  33461:      2         5741

26  37666:     29          433

27  43261:      5         2897

28  51641:     13         1325

29  62210:     89          233

30  75025:      1        28657

...

CROSSREFS

Cf. A002559.

Sequence in context: A093664 A298212 A087620 * A262213 A178913 A142721

Adjacent sequences:  A253806 A253807 A253808 * A253810 A253811 A253812

KEYWORD

nonn,tabf

AUTHOR

Wolfdieter Lang, Jan 28 2015

STATUS

approved

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Last modified July 28 11:11 EDT 2021. Contains 346326 sequences. (Running on oeis4.)