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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A059499 a(n) = |{m : multiplicative order of 2 mod m = n}|. 20
1, 1, 1, 2, 1, 3, 1, 4, 2, 5, 3, 16, 1, 5, 5, 8, 1, 24, 1, 38, 9, 11, 3, 68, 6, 5, 4, 54, 7, 79, 1, 16, 11, 5, 13, 462, 3, 5, 13, 140, 3, 123, 7, 110, 54, 11, 7, 664, 2, 114, 29, 118, 7, 124, 59, 188, 13, 55, 3, 4456, 1, 5, 82, 96, 5, 353, 3, 118, 11, 485, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

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). See A002326.

a(n) is odd iff n is squarefree, A005117. - Thomas Ordowski, Jan 18 2014

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..200

FORMULA

a(n) = 1 iff 2^n-1 is noncomposite. a(prime(n)) = 2^A088863(n)-1. - Thomas Ordowski, Jan 16 2014

EXAMPLE

a(3) = |{7}| = 1, a(4) = |{5,15}| = 2, a(6) = |{9,21,63}| = 3.

MAPLE

with(numtheory):

a:= n-> add(mobius(n/d)*tau(2^d-1), d=divisors(n)):

seq(a(n), n=1..100);  # Alois P. Heinz, May 31 2012

MATHEMATICA

a[n_] := Sum[ MoebiusMu[n/d] * DivisorSigma[0, 2^d - 1], {d, Divisors[n]}]; Table[a[n], {n, 1, 71} ] (* Jean-Fran├žois Alcover, Dec 12 2012 *)

CROSSREFS

Cf. A001037, A058943, A059912.

Column k=2 of A212957. - Alois P. Heinz, Oct 12 2012

Sequence in context: A100053 A029194 A246582 * A113322 A007380 A319162

Adjacent sequences:  A059496 A059497 A059498 * A059500 A059501 A059502

KEYWORD

easy,nonn

AUTHOR

Vladeta Jovovic, Feb 04 2001

EXTENSIONS

More terms from John W. Layman, Mar 22 2002

More terms from Alois P. Heinz, May 31 2012

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 November 20 06:06 EST 2018. Contains 317385 sequences. (Running on oeis4.)