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!)
A054412 Numbers n such that, in the prime factorization of n, the product of exponents equals the product of prime factors. 14

%I #27 Apr 11 2020 05:30:54

%S 1,4,27,72,108,192,800,1458,3125,5120,6272,12500,21600,30375,36000,

%T 48600,77760,84375,114688,116640,121500,138240,169344,225000,247808,

%U 337500,384000,395136,600000,653184,750141,823543,857304,979776,1384448,1474560,1500000

%N Numbers n such that, in the prime factorization of n, the product of exponents equals the product of prime factors.

%C For p prime, numbers of the form p^p satisfy the condition, hence A051674 is a subsequence. - _Michel Marcus_, May 19 2014

%C Also, numbers of the form p^q * q^p, with distinct primes p and q, satisfy the condition, hence A082949 is a subsequence. - _Bernard Schott_, Apr 11 2020

%H Rémy Sigrist, <a href="/A054412/b054412.txt">Table of n, a(n) for n = 1..10000</a>

%H Rémy Sigrist, <a href="/A054412/a054412.gp.txt">PARI program for A054412</a>

%e 192 is included because 192 =2^6 *3^1 and 2*3 = 6*1.

%t peppfQ[n_]:=Module[{f=Transpose[FactorInteger[n]]},Times@@First[f] == Times@@Last[f]]; Select[Range[1.5*10^6],peppfQ] (* _Harvey P. Dale_, Oct 14 2015 *)

%o (PARI) isok(n) = my(f = factor(n)); prod(i=1, #f~, f[i,2]) == prod(i=1, #f~, f[i,1]); \\ _Michel Marcus_, May 19 2014

%o (PARI) See Links section.

%Y Cf. A051674, A054411, A082949.

%K nonn

%O 1,2

%A _Leroy Quet_, May 09 2000

%E More terms from _James A. Sellers_, May 23 2000

%E New name and three more terms from _Michel Marcus_, May 19 2014

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 April 24 04:02 EDT 2024. Contains 371918 sequences. (Running on oeis4.)