login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A059887 a(n) = |{m : multiplicative order of 5 mod m=n}|. 3
3, 5, 3, 12, 9, 37, 3, 28, 18, 47, 3, 180, 3, 53, 81, 176, 9, 446, 21, 564, 39, 117, 9, 884, 180, 53, 360, 244, 21, 5959, 9, 800, 39, 111, 369, 9536, 21, 483, 39, 5476, 9, 18289, 9, 1140, 2958, 111, 3, 9424, 6, 3852, 177, 884, 21, 81048, 561, 1188, 69, 227, 9 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The multiplicative order of a mod m, gcd(a,m)=1, is the smallest natural number d for which a^d = 1 (mod m). a(n) = number of orders of degree-n monic irreducible polynomials over GF(5).

LINKS

Table of n, a(n) for n=1..59.

FORMULA

a(n) = Sum_{d|n} mu(n/d)*tau(5^d-1), (mu(n) = Moebius function A008683, tau(n) = number of divisors of n A000005).

MAPLE

with(numtheory):

a:= n-> add(mobius(n/d)*tau(5^d-1), d=divisors(n)):

seq(a(n), n=1..50);  # Alois P. Heinz, Oct 12 2012

CROSSREFS

Cf. A000005, A008683, A001692, A053447, A058945, A059499, A059885, A059886, A059888-A059892, A212485.

Column k=5 of A212957. - Alois P. Heinz, Oct 12 2012

Sequence in context: A178095 A177904 A049072 * A023585 A089948 A023583

Adjacent sequences:  A059884 A059885 A059886 * A059888 A059889 A059890

KEYWORD

easy,nonn

AUTHOR

Vladeta Jovovic, Feb 06 2001

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified February 18 17:08 EST 2018. Contains 299325 sequences. (Running on oeis4.)