A214720 - OEIS

%I #11 Mar 30 2014 12:13:32

%S 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,

%T 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,

%U 2,3,2,5,2,3,2,3,2,5,2,3,2,3,2,5,2,3,2

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

%H Clark Kimberling, <a href="/A214720/b214720.txt">Table of n, a(n) for n = 1..1000</a>

%e a(12) = 5 because of the following:

%e gcd(144-1,11) > 1,

%e gcd(144-2,10) > 1 ,

%e gcd(144-3,9) > 1,

%e gcd(144-4,8) >1,

%e gcd(144-5,7) = 1.

%p A214720 := proc(n)

%p     for m from 1 do

%p         if igcd(n^2-m,n-m) =1  then

%p             return m;

%p         end if;

%p     end do:

%p end proc: # _R. J. Mathar_, Mar 30 2014

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

%Y Cf. A214716, A053669.

%K nonn,easy

%O 1,1

%A _Clark Kimberling_, Jul 27 2012