OFFSET
1,1
COMMENTS
Numbers k such that k/A007947(k) = A006530(k) where A007947 is the product of the distinct prime factors of k and A006530 is the greatest prime dividing k.
The numbers of the form p^2 with p prime, or of the form p_1*p_2*...*p_k*p^2 with p_i primes < p prime are in the sequence.
All these numbers are round numbers (their greatest prime factor is <= their square root). - Emmanuel Vantieghem, Feb 22 2017
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
MAPLE
with(numtheory) :for n from 2 to 2000 do:x:=factorset(n):n1:=nops(x): p:= product('x[i]', 'i'=1..n1):m:=n/p:if m=x[n1] then printf(`%d, `, n):else fi:od:
MATHEMATICA
rad[n_]:=Times@@(First@#&/@FactorInteger@n); Select[Range[2, 2000], FactorInteger[#][[-1, 1]]==#/rad[#]&]
gpQ[n_]:=Module[{pf=Transpose[FactorInteger[n]][[1]]}, n/Times@@pf == Last[ pf]]; Select[Range[2, 2000], gpQ] (* Harvey P. Dale, Aug 16 2014 *)
PROG
(PARI) isok(n) = my(f = factor(n)); n/factorback(f[, 1]) == f[#f~, 1]; \\ Michel Marcus, Aug 16 2014
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Michel Lagneau, Sep 11 2013
STATUS
approved