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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.
4
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
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. A020491 (positions of 1's), A342665 (fixed points).
Sequence in context: A088964 A326721 A243792 * A242885 A181157 A095248
KEYWORD
nonn
AUTHOR
Leroy Quet and Ray Chandler, Oct 26 2006
STATUS
approved