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A214720 Least m>0 such that n^2-m and n-m are relatively prime. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified April 12 11:36 EDT 2021. Contains 342920 sequences. (Running on oeis4.)