%I #22 Apr 01 2021 14:43:18

%S 1,2,1,4,1,3,1,1,1,1,1,6,1,7,1,8,1,1,1,4,1,11,1,1,25,1,9,1,1,1,1,16,1,

%T 1,1,4,1,19,1,1,1,7,1,4,1,23,1,12,1,5,1,1,1,3,1,1,1,1,1,5,1,31,1,16,1,

%U 11,1,4,1,1,1,1,1,1,25,1,1,1,1,4,81,1,1,1,1,43,1,1,1,1,1,4,1,47,1,24,1,1,1

%N a(n) is the ((phi(n) mod d(n)) + 1)-th positive divisor of n, where phi(n) is number of positive integers which are <= n and are coprime to n and d(n) is the number of positive divisors of n.

%H Antti Karttunen, <a href="/A124331/b124331.txt">Table of n, a(n) for n = 1..16384</a>

%t f[n_] := Block[{d = Divisors[n]}, d[[Mod[EulerPhi[n], Length[d]] + 1]]];Table[f[n], {n, 100}] (* _Ray Chandler_, Oct 26 2006 *)

%o (PARI) A124331(n) = { my(m=eulerphi(n)%numdiv(n), ds=divisors(n)); ds[1+m]; }; \\ _Antti Karttunen_, Mar 30 2021

%Y Cf. A000005, A000010, A124219, A124330.

%Y Cf. A020491 (positions of 1's), A342665 (fixed points).

%K nonn

%O 1,2

%A _Leroy Quet_ and _Ray Chandler_, Oct 26 2006