OFFSET
1,2
COMMENTS
All numbers of the form 3^k2*5^k3*...*p_n^k_n, where k2 >= k3 >= ... >= k_n, sorted.
LINKS
Ray Chandler, Table of n, a(n) for n = 1..10000
David Ryan, Mathematical Harmony Analysis, arXiv preprint arXiv:1603.08904 [cs.SD], 2016-2017.
FORMULA
Sum_{n>=1} 1/a(n) = Product_{n>=2} 1/(1 - 1/A070826(n)) = 1.6241170949... - Amiram Eldar, Oct 20 2020
MATHEMATICA
PrimeExponents[n_] := FactorInteger[n][[All, 2]]; lpe = {}; A147516 = {1}; Do[pe = PrimeExponents[n] // Sort; If[FreeQ[lpe, pe], AppendTo[lpe, pe]; AppendTo[A147516, n]], {n, 3, 40000, 2}]; A147516 (* Jean-François Alcover, Jan 27 2015, after Robert G. Wilson v *)
PROG
(PARI) is(n)=my(k=oo, t); forprime(p=3, , t=valuation(n, p); if(t>k, return(0), k=t); if(k, n/=p^k, return(n==1))) \\ Charles R Greathouse IV, Aug 20 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Will Nicholes, Nov 05 2008
EXTENSIONS
Edited and extended by Ray Chandler, Jul 29 2010
STATUS
approved