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A205793 Least positive integer k such that n divides C(k)-C(j) for some j in [1,k-1], where C=A002808 (composite numbers). 1
2, 2, 4, 3, 4, 5, 8, 6, 8, 7, 8, 9, 12, 10, 12, 11, 12, 13, 15, 14, 15, 16, 17, 18, 21, 19, 21, 20, 21, 22, 23, 24, 26, 25, 26, 27, 30, 28, 30, 29, 30, 31, 33, 32, 33, 34, 35, 36, 38, 37, 38, 39, 40, 41, 44, 42, 44, 43, 44, 45, 46, 47, 49, 48, 49, 50, 53, 51, 53, 52 (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..70.

EXAMPLE

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

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

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

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

5 divides C(4)-C(1) -> k=4, j=1

6 divides C(5)-C(1) -> k=5, j=1

MATHEMATICA

s = Select[Range[2, 120], ! PrimeQ[#] &]

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.

Sequence in context: A177235 A079707 A233511 * A178431 A233574 A157927

Adjacent sequences:  A205790 A205791 A205792 * A205794 A205795 A205796

KEYWORD

nonn

AUTHOR

Clark Kimberling, Feb 01 2012

STATUS

approved

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Last modified February 24 01:16 EST 2020. Contains 332195 sequences. (Running on oeis4.)