A161888 a(n) = the smallest positive integer that does not divide n, and is such that sum{k=1 to n} a(k) is coprime to n.

2, 3, 2, 6, 3, 7, 2, 6, 4, 4, 2, 8, 2, 4, 4, 6, 2, 4, 2, 6, 4, 4, 2, 14, 3, 3, 4, 8, 2, 4, 2, 6, 2, 4, 2, 8, 2, 4, 4, 6, 2, 4, 2, 6, 6, 4, 2, 10, 2, 4, 2, 6, 2, 4, 3, 3, 4, 4, 2, 8, 2, 4, 4, 6, 3, 5, 2, 6, 2, 8, 2, 10, 2, 4, 4, 6, 3, 9, 2, 6, 4, 4, 2, 8, 3, 3, 4, 6, 2, 4, 2, 6, 4, 4, 3, 5, 2, 4, 2, 8, 2, 8, 2, 6, 2

Offset

1,1

Comments

Sum{k=1 to n} a(k) = A161889(n).

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Mathematica

spi[{n_, s_, a_}]:=Module[{k=1}, While[Divisible[n+1, k]||!CoprimeQ[s+k, n+1], k++]; {n+1, s+k, k}]; Transpose[NestList[spi, {1, 2, 2}, 105]][[3]] (* Harvey P. Dale, May 26 2015 *)

Crossrefs

Cf. A161889

Sequence in context: A134060 A329282 A197289 * A347859 A157224 A097914

Adjacent sequences: A161885 A161886 A161887 * A161889 A161890 A161891

Keyword

nonn

Author

Leroy Quet, Jun 21 2009

Extensions

More terms from Sean A. Irvine, Aug 10 2010

Status

approved