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A214074
Least m>0 such that 2^n-m and 3^n-m are relatively prime.
5
1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 1, 1, 2, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 1, 2, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1, 2, 2, 1, 1, 2
OFFSET
1,4
COMMENTS
Conjecture: a(n) = 3 if and only if n = 330*k-209 for some k>=1.
LINKS
EXAMPLE
gcd(64-1,729-1) = 7 and gcd(64-2,729-2) = 1, so a(6) = 2.
MATHEMATICA
Table[m = 1; While[GCD[2^n - m, 3^n - m] != 1, m++]; m, {n, 1, 140}]
CROSSREFS
Cf. A214180.
Sequence in context: A095772 A305392 A175301 * A003640 A359944 A359308
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jul 27 2012
STATUS
approved