A124331 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.

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, 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, 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

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..16384

Mathematica

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

Prog

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

Crossrefs

Cf. A000005, A000010, A124219, A124330.

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

Sequence in context: A088964 A326721 A243792 * A242885 A181157 A095248

Adjacent sequences: A124328 A124329 A124330 * A124332 A124333 A124334

Keyword

nonn

Author

Leroy Quet and Ray Chandler, Oct 26 2006

Status

approved