A214716 Least m>0 such that 3^n-m and n-m are relatively prime.

2, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 4, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 4

Offset

1,1

Links

Clark Kimberling, Table of n, a(n) for n = 1..1000

Example

gcd(3^7-1,6) = 2, gcd(3^7-2,5) = 5, gcd(3^7-3,4) = 4, gcd(3^7-4,3) = 1, so a(7) = 4.

Mathematica

Table[m = 1; While[GCD[3^n - m, n - m] != 1, m++]; m, {n, 1, 140}]
lm[n_]:=Module[{m=1, n3=3^n}, While[!CoprimeQ[n3-m, n-m], m++]; m]; Array[ lm, 90] (* Harvey P. Dale, May 10 2016 *)

Crossrefs

Cf. A214071, A214717.

Sequence in context: A058232 A216320 A308455 * A116933 A354060 A194448

Adjacent sequences: A214713 A214714 A214715 * A214717 A214718 A214719

Keyword

nonn,easy

Author

Clark Kimberling, Jul 27 2012

Status

approved