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A205785 Least positive integer k such that n divides C(k)-C(j) for some j in [1,k-1], where C=A205825. 2
2, 3, 4, 5, 4, 5, 6, 5, 4, 4, 4, 6, 6, 8, 7, 7, 5, 5, 5, 6, 8, 7, 7, 8, 6, 7, 6, 9, 12, 7, 11, 9, 7, 10, 8, 6, 12, 7, 6, 8, 16, 8, 8, 9, 7, 12, 15, 9, 8, 6, 10, 7, 9, 6, 10, 9, 9, 12, 6, 8, 14, 11, 10, 9, 8, 7, 9, 10, 7, 8, 13, 10, 8, 12, 11, 14, 10, 8, 12, 10, 10, 16, 8, 9, 10, 14 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For a guide to related sequences, see A204892.

LINKS

Table of n, a(n) for n=1..86.

EXAMPLE

1 divides C(2)-C(1) -> k=2, j=1

2 divides C(3)-C(1) -> k=3, j=1

3 divides C(4)-C(3) -> k=4, j=3

4 divides C(5)-C(4) -> k=5, j=4

5 divides C(4)-C(2) -> k=4, j=2

MATHEMATICA

s = Table[n!/Ceiling[n/2]!, {n, 1, 120}];

lk = Table[

  NestWhile[# + 1 &, 1,

   Min[Table[Mod[s[[#]] - s[[j]], z], {j, 1, # - 1}]] =!= 0 &], {z, 1,

    Length[s]}]

Table[NestWhile[# + 1 &, 1,

  Mod[s[[lk[[j]]]] - s[[#]], j] =!= 0 &], {j, 1, Length[lk]}]

(* Peter J. C. Moses, Jan 27 2012 *)

CROSSREFS

Cf. A204892, A205825.

Sequence in context: A204982 A017850 A291520 * A282062 A276073 A284000

Adjacent sequences:  A205782 A205783 A205784 * A205786 A205787 A205788

KEYWORD

nonn

AUTHOR

Clark Kimberling, Feb 01 2012

STATUS

approved

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Last modified February 18 03:28 EST 2018. Contains 299298 sequences. (Running on oeis4.)