OFFSET
1,3
COMMENTS
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
PROG
(Scheme, with memoization-macro definec)
(Python)
from operator import mul
from sympy import primefactors
from sympy.ntheory.factor_ import core
from functools import reduce
def a007947(n): return 1 if n<2 else reduce(mul, primefactors(n))
def a013928(n): return sum(1 for i in range(1, n) if core(i) == i)
print([a013928(a007947(n)) for n in range(1, 101)]) # Indranil Ghosh, Apr 18 2017
(Python)
from math import prod, isqrt
from sympy import primefactors, mobius
def A285329(n):
m=prod(primefactors(n))-1
return sum(mobius(k)*(m//k**2) for k in range(1, isqrt(m)+1)) # Chai Wah Wu, May 12 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 17 2017
STATUS
approved