login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A100995 If n is a prime power p^m, m >= 1, then m, otherwise 0. 31
0, 1, 1, 2, 1, 0, 1, 3, 2, 0, 1, 0, 1, 0, 0, 4, 1, 0, 1, 0, 0, 0, 1, 0, 2, 0, 3, 0, 1, 0, 1, 5, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 2, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 6, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 4, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Calculate matrix powers: (A175992^1)/1 - (A175992^2)/2 + (A175992^3)/3 - (A175992^4)/4 + ... Then the nonzero values of a(n) are found as reciprocals in the first column. Compare this to the Taylor series for log(1+x) = (x)/1 - (x^2)/2 + (x^3)/3 - (x^4)/4 + ... Therefore it is natural to write 0, 1/1, 1/1, 1/2, 1/1, 0, 1/1, 1/3, 1/2, 0, 1/1, ... Raising n to a such power gives A014963. - Mats Granvik, Gary W. Adamson, Apr 04 2011

The Dirichlet series that generates the reciprocals of this sequence is the logarithm of the Riemann zeta function. - Mats Granvik, Gary W. Adamson, Apr 04 2011

Number of automorphisms of the finite field with n elements, or 0 if the field does not exist. For n=p^k where p is a prime and k is integer, the automorphism group of the finite field with n elements is a cyclic group of order k generated by the Frobenius endomorphism. - Yancheng Lu, Jan 11 2021

LINKS

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

FORMULA

A100994(n) = A014963(n)^a(n);

a(A000961(n)) = A025474(n).

a(n) = Sum_{d|n, gcd(d, n/d) = 1} (-1)^omega(n/d) * bigomega(d). - Ilya Gutkovskiy, Apr 15 2021

MAPLE

f:= proc(n) local F;

    F:= ifactors(n)[2];

    if nops(F) = 1 then F[1][2]

    else 0

    fi

end proc:

map(f, [$1..100]); # Robert Israel, Jun 09 2015

MATHEMATICA

ppm[n_]:=If[PrimePowerQ[n], FactorInteger[n][[1, 2]], 0]; Array[ppm, 110] (* Harvey P. Dale, Mar 03 2014 *)

a=Table[Limit[Sum[If[Mod[n, k] == 0, MoebiusMu[n/k]/(n/k)^(s - 1)/(1 - 1/n^(s - 1)), 0], {k, 1, n}], s -> 1], {n, 1, 105}];

Numerator[a]*Denominator[a] (* Mats Granvik, Jun 09 2015 *)

a = FullSimplify[Table[MangoldtLambda[n]/Log[n], {n, 1, 105}]]

Numerator[a]*Denominator[a] (* Mats Granvik, Jun 09 2015 *)

PROG

(PARI) {a(n) = my(t); if( n<1, 0, t = factor(n); if( [1, 2] == matsize(t), t[1, 2], 0))} /* Michael Somos, Aug 15 2012 */

(PARI) {a(n) = my(t); if( n<1, 0, if( t = isprimepower(n), t))} /* Michael Somos, Aug 15 2012 */

(Haskell)

a100995 n = f 0 n where

   f e 1 = e

   f e x = if r > 0 then 0 else f (e + 1) x'

           where (x', r) = divMod x p

   p = a020639 n

-- Reinhard Zumkeller, Mar 19 2013

CROSSREFS

Cf. A028233, A069513, A010055.

Sequence in context: A171963 A292131 A255740 * A319273 A329615 A272894

Adjacent sequences:  A100992 A100993 A100994 * A100996 A100997 A100998

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Nov 26 2004

EXTENSIONS

Edited by Daniel Forgues and N. J. A. Sloane, Aug 18 2009

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 4 11:49 EDT 2022. Contains 355075 sequences. (Running on oeis4.)