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

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

Cf. A214074, A214707.

Sequence in context: A070304 A275308 A233138 * A083952 A245225 A214860

Adjacent sequences: A214705 A214706 A214707 * A214709 A214710 A214711

Keyword

nonn,easy

Author

Clark Kimberling, Jul 27 2012

Status

approved