A259579 - OEIS

A259579

Number of distinct differences in row n of the reciprocity array of 2.

1, 2, 3, 2, 1, 4, 3, 4, 5, 4, 3, 6, 3, 4, 5, 6, 3, 6, 3, 6, 7, 6, 3, 10, 3, 6, 7, 8, 3, 12, 3, 8, 9, 6, 5, 12, 3, 6, 9, 10, 3, 12, 3, 10, 9, 6, 3, 16, 5, 8, 9, 10, 3, 10, 5, 10, 9, 6, 3, 20, 3, 6, 9, 10, 5, 14, 3, 10, 9, 12, 3, 16, 3, 6, 11, 10, 9, 14, 3, 14

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OFFSET

1,2

COMMENTS

The "reciprocity law" that Sum{[(n*k+x)/m] : k = 0..m} = Sum{[(m*k+x)/n] : k = 0..n} where x is a real number and m and n are positive integers, is proved in Section 3.5 of Concrete Mathematics (see References). See A259572 for a guide to related sequences.

REFERENCES

R. L. Graham, D. E. Knuth, O. Patashnik, Concrete Mathematics, Addison-Wesley, 1989, pages 90-94.

LINKS

Table of n, a(n) for n=1..80.

EXAMPLE

In the array at A259578, row 6 is (2,5,6,10,12,15,17,20,21,25,27,...), with differences (3,1,4,2,3,2,3,1,4,2,...), and distinct differences {1,2,3,4}, so that a(4) = 4.

MATHEMATICA

x = 2; s[m_, n_] := Sum[Floor[(n*k + x)/m], {k, 0, m - 1}];

t[m_] := Table[s[m, n], {n, 1, 1000}];

u = Table[Length[Union[Differences[t[m]]]], {m, 1, 120}]

CROSSREFS

Cf. A249572, A249577, A259580.

Sequence in context: A343180 A129773 A105789 * A076549 A373419 A210500

Adjacent sequences: A259576 A259577 A259578 * A259580 A259581 A259582

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Jul 17 2015

STATUS

approved