OFFSET
1,8
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
EXAMPLE
PROG
(PARI) a(n) = my(f=factor(n)); numdiv(n) - bigomega(n) - prod(k=1, #f~, f[k, 2]); \\ Michel Marcus, May 25 2017
(Python)
from sympy import primefactors, factorint, divisor_count
from operator import mul
def bigomega(n): return 0 if n==1 else bigomega(n/primefactors(n)[0]) + 1
def a005361(n):
f=factorint(n)
return 1 if n==1 else reduce(mul, [f[i] for i in f])
def a(n): return divisor_count(n) - bigomega(n) - a005361(n) # Indranil Ghosh, May 25 2017
CROSSREFS
KEYWORD
sign
AUTHOR
Labos Elemer, Mar 28 2003
STATUS
approved