A205782 Least positive integer k such that n divides C(k)-C(j) for some j in [1,k-1], where C=A205824.

2, 3, 2, 4, 3, 3, 4, 5, 2, 3, 5, 5, 6, 4, 3, 6, 7, 3, 8, 4, 5, 5, 9, 6, 4, 6, 3, 4, 11, 3, 3, 7, 5, 7, 4, 5, 7, 8, 6, 6, 12, 5, 6, 5, 3, 9, 9, 6, 6, 4, 7, 6, 7, 3, 6, 5, 8, 11, 18, 6, 7, 10, 5, 7, 7, 5, 9, 7, 9, 4, 18, 6, 17, 7, 8, 8, 5, 6, 18, 7, 10, 12, 12, 5, 7, 6, 11, 6, 13, 3, 6, 9, 3

Offset

1,1

Comments

For a guide to related sequences, see A204892.

Links

Table of n, a(n) for n=1..93.

Example

1 divides C(2)-C(1) -> k=2, j=1
2 divides C(3)-C(2) -> k=3, j=2
3 divides C(2)-C(1) -> k=2, j=1
4 divides C(4)-C(3) -> k=4, j=3
5 divides C(3)-C(2) -> k=3, j=2

Mathematica

s = Table[(3 n)!/(3 n*n!*(n + 1)!), {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, A205824.

Sequence in context: A361660 A318046 A246348 * A070296 A303581 A216647

Adjacent sequences: A205779 A205780 A205781 * A205783 A205784 A205785

Keyword

nonn

Author

Clark Kimberling, Feb 01 2012

Status

approved