A214720 Least m>0 such that n^2-m and n-m are relatively prime.

2, 1, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2

Offset

1,1

Links

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

Example

a(12) = 5 because of the following:
gcd(144-1,11) > 1,
gcd(144-2,10) > 1 ,
gcd(144-3,9) > 1,
gcd(144-4,8) >1,
gcd(144-5,7) = 1.

Maple

A214720 := proc(n)
    for m from 1 do
        if igcd(n^2-m, n-m) =1  then
            return m;
        end if;
    end do:
end proc: # R. J. Mathar, Mar 30 2014

Mathematica

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

Crossrefs

Cf. A214716, A053669.

Sequence in context: A250099 A241949 A288126 * A035368 A249686 A107853

Adjacent sequences: A214717 A214718 A214719 * A214721 A214722 A214723

Keyword

nonn,easy

Author

Clark Kimberling, Jul 27 2012

Status

approved