A214708 - OEIS

A214708

Least m>0 such that 4^n-m and 5^n-m are relatively prime.

1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 2, 2, 2, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2

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OFFSET

1,2

COMMENTS

a(248) = 3. Is every term < 4?

LINKS

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

EXAMPLE

gcd(256-1,625-1) = 3 and gcd(256-2, 625-2) = 1, so a(4) = 2.

MATHEMATICA

Table[m = 1; While[GCD[4^n - m, 5^n - m] != 1, m++]; m, {n, 1, 140}]

CROSSREFS