OFFSET
1,1
COMMENTS
Numbers n for which A065642(n) < A285109(n). Positions of terms > 1 in A285337. - Antti Karttunen, Apr 19 2017
For any n in this sequence, k*n is also in this sequence. No term is squarefree. For any distinct primes p and q with p > q, p^2*q and p*q^(ceiling(log_q(p))) are in this sequence. - Charlie Neder, Oct 29 2018
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
MATHEMATICA
Select[Range[2, 300], Function[{n, c, lpf}, SelectFirst[Range[n + 1, n^2], Times @@ FactorInteger[#][[All, 1]] == c &] < n lpf] @@ {#1, Times @@ #2, #2[[1]]} & @@ {#, FactorInteger[#][[All, 1]]} &] (* Michael De Vlieger, Oct 31 2018 *)
PROG
(PARI) for(n=1, 300, for(k=1, n^2-n, a=factorback(factorint(n)[, 1]); b=factorback(factorint(n+k)[, 1]); c=vecmin(factor(n)[, 1]); if(a==b&&n+k<n*c&!print1(n", ")&break)))
(PARI)
A020639(n) = if(1==n, n, vecmin(factor(n)[, 1]));
A007947(n) = factorback(factorint(n)[, 1]); \\ From Andrew Lelechenko, May 09 2014
n=0; k=1; while(k <= 10000, n=n+1; if(isA284342(n), write("b284342.txt", k, " ", n); k=k+1));
\\ Antti Karttunen, Apr 19 2017
(Python)
from operator import mul
from sympy import primefactors
from functools import reduce
def a007947(n): return 1 if n<2 else reduce(mul, primefactors(n))
def a065642(n):
if n==1: return 1
r=a007947(n)
n = n + r
while a007947(n)!=r:
n+=r
return n
print([n for n in range(10, 301) if a065642(n)<n*min(primefactors(n))]) # Indranil Ghosh, Apr 20 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Gionata Neri, Mar 25 2017
STATUS
approved