A069513 Characteristic function of the prime powers p^k, k >= 1.

0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0

Offset

1,1

Comments

Also, number of Galois fields of order n. - Charles R Greathouse IV, Mar 12 2008

Also, number of abelian indecomposable groups of order n. - Kevin Lamoreau, Mar 13 2023

Links

Daniel Forgues, Table of n, a(n) for n = 1..100000.

Formula

If n >= 2, a(n) = A010055(n).

a(n) = Sum_{d|n} bigomega(d)*mu(n/d); equivalently, Sum_{d|n} a(d) = bigomega(n); equivalently, Möbius transform of bigomega(n).

Dirichlet g.f.: ppzeta(s). Here ppzeta(s) = Sum_{p prime} Sum_{k>=1} 1/(p^k)^s. Note that ppzeta(s) = Sum_{p prime} 1/(p^s - 1) = Sum_{k>=1} primezeta(k*s). - Franklin T. Adams-Watters, Sep 11 2005

a(n) = floor(1/A001221(n)), for n > 1. - Enrique Pérez Herrero, Jun 01 2011

Maple

A069513 := proc(n)
    if n = 1 then
        0 ;
    elif A001221(n) > 1 then
        0;
    else
        1 ;
    end if ;
end proc:
seq(A069513(n), n=1..80) ; # R. J. Mathar, Nov 02 2016

Mathematica

A069513[n_]:=Boole[PrimeNu[n]==1]; A069513/@Range[20] (* Enrique Pérez Herrero, May 30 2011 *)

Prog

(PARI) for(n=1, 120, print1(omega(n)==1, ", "))
(Haskell)
a069513 1 = 0
a069513 n = a010055 n  -- Reinhard Zumkeller, Mar 19 2013
(Python)
from sympy import primefactors
def A069513(n): return int(len(primefactors(n)) == 1) # Chai Wah Wu, Mar 31 2023

Crossrefs

Cf. A246655, A010055, A001222, A008683, A090751, A000688, A361414.

The partial sums of this sequence give A025528. - Daniel Forgues, Mar 02 2009

Cf. A014963, A003418. - Enrique Pérez Herrero, Jun 01 2011

Sequence in context: A189727 A361113 A268411 * A092248 A354920 A106743

Adjacent sequences: A069510 A069511 A069512 * A069514 A069515 A069516

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 15 2002

Extensions

Moved original definition to formula line. Used comment (that I previously added) as definition. - Daniel Forgues, Mar 08 2009

Edited by Franklin T. Adams-Watters, Nov 02 2009

Status

approved