A214057 Least m>0 such that 2^n-1+m and n-m have a common divisor > 1.

1, 2, 1, 4, 1, 3, 1, 8, 1, 10, 1, 3, 1, 14, 1, 16, 1, 3, 1, 5, 1, 2, 1, 3, 1, 26, 1, 28, 1, 3, 1, 4, 1, 6, 1, 2, 1, 15, 1, 5, 1, 2, 1, 5, 1, 17, 1, 3, 1, 50, 1, 8, 1, 2, 1, 56, 1, 58, 1, 3, 1, 2, 1, 6, 1, 3, 1, 31, 1, 70, 1, 3, 1, 4, 1, 6, 1, 3, 1, 5, 1, 2, 1

Offset

1,2

Links

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

Example

gcd(2^6-1-1,6-1) = gcd(62,5) = 1
gcd(2^6-1-2,6-2) = gcd(61,4) = 1
gcd(2^6-1-3,6-3) = gcd(60,3) = 3,
so that a(6) = 3.

Mathematica

b[n_] := 2^n-1; c[n_] := n;
Table[m = 1; While[GCD[b[n] + m, c[n] - m] == 1, m++]; m, {n, 1, 100}]

Crossrefs

Cf. A214056.

Sequence in context: A127461 A329900 A101261 * A067614 A341308 A353359

Adjacent sequences: A214054 A214055 A214056 * A214058 A214059 A214060

Keyword

nonn,easy

Author

Clark Kimberling, Jul 22 2012

Status

approved