OFFSET
1,3
COMMENTS
The scatter plot has unusual "rays".
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
MATHEMATICA
Table[n - If[n <= 2, n - 1, Module[{k = n - 2, e = Floor@ Log2@ n}, While[PowerMod[n, e, k] != 0, k--]; k]], {n, 100}] (* Michael De Vlieger, Apr 26 2017 *)
PROG
(Python)
from sympy import divisors
from sympy.ntheory.factor_ import core
def a007947(n): return max(i for i in divisors(n) if core(i) == i)
def a079277(n):
k=n - 1
while True:
if a007947(k*n) == a007947(n): return k
else: k-=1
def a(n): return 1 if n<2 else n - a079277(n)
print([a(n) for n in range(1, 101)]) # Indranil Ghosh, Apr 26 2017
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Antti Karttunen, Apr 26 2017
STATUS
approved