OFFSET
1,3
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
Factorizations of the n-th cyclotomic polynomial over GF(7) for n <= 10:
n = 1: x - 1;
n = 2: x + 1;
n = 3: (x + 3)*(x - 2);
n = 4: x^2 + 1;
n = 5: x^4 + x^3 + x^2 + x + 1;
n = 6: (x + 2)*(x - 3);
n = 7: (x - 1)^6;
n = 8: (x^2 + 3x + 1)*(x^2 - 3x + 1);
n = 9: (x^3 + 3)*(x^3 - 2);
n = 10: x^4 - x^3 + x^2 - x^2 + 1.
MATHEMATICA
a[n_] := EulerPhi[n] / MultiplicativeOrder[7, n / 7^IntegerExponent[n, 7]]; Array[a, 100] (* Amiram Eldar, Jul 21 2024 *)
PROG
(PARI) a(n) = my(s=n/7^valuation(n, 7)); eulerphi(n)/znorder(Mod(7, s))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jianing Song, Sep 26 2019
STATUS
approved