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A215619 a(n) is the number of consecutive terms of A100071, beginning with index n, which are divisible by n. 1
4, 1, 6, 1, 8, 1, 4, 1, 12, 5, 14, 1, 4, 1, 18, 1, 20, 1, 4, 1, 24, 1, 6, 1, 4, 1, 30, 21, 32, 1, 12, 1, 8, 1, 38, 1, 14, 1, 42, 1, 44, 1, 6, 1, 48, 1, 8, 1, 4, 1, 54, 1, 6, 9, 4, 1, 60, 1, 62, 1, 4, 1, 6, 1, 68, 1, 4, 1, 72, 1, 74, 1, 4, 1, 12, 1, 80, 1, 4, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

COMMENTS

a(n) = n+1 iff n is prime.

a(n) = 1  iff n in { A067315 }.

1 <= a(n) <= n+1.

{ n : a(2n)>1 } = { A058008 } \ { 1 }.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 3..1000

MAPLE

b:= proc(n) b(n):= n * binomial(n-1, floor((n-1)/2)) end:

a:= proc(n) local k;

      for k from 0 while irem(b(n+k), n)=0 do od; k

    end:

seq (a(n), n=3..100);  # Alois P. Heinz, Aug 17 2012

MATHEMATICA

b[n_] := n Binomial[n-1, Floor[(n-1)/2]];

a[n_] := Module[{k = 0}, While[Mod[b[n+k], n] == 0, k++]; k];

a /@ Range[3, 100] (* Jean-Fran├žois Alcover, Nov 22 2020, after Alois P. Heinz *)

CROSSREFS

Cf. A000040, A067315, A100071.

Sequence in context: A144907 A185093 A010779 * A136706 A326478 A324118

Adjacent sequences:  A215616 A215617 A215618 * A215620 A215621 A215622

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Aug 17 2012

STATUS

approved

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Last modified March 8 11:28 EST 2021. Contains 341948 sequences. (Running on oeis4.)