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A214057 Least m>0 such that 2^n-1+m and n-m have a common divisor > 1. 3
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 (list; graph; refs; listen; history; text; internal format)
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 A113901

Adjacent sequences:  A214054 A214055 A214056 * A214058 A214059 A214060

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Jul 22 2012

STATUS

approved

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Last modified April 19 09:52 EDT 2021. Contains 343110 sequences. (Running on oeis4.)