OFFSET
1,4
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
The a(n) divisors for selected n:
n = 1: 2: 4: 6: 24: 30: 36: 60: 96: 144: 210: 216: 240: 360:
---------------------------------------------------------------------
{} 2 2 2 2 2 2 2 2 2 2 2 2 2
4 3 3 3 3 3 3 3 3 3 3 3
6 4 5 4 4 4 4 5 4 4 4
6 30 6 5 6 6 6 6 5 5
24 9 6 8 8 7 8 6 6
36 10 12 9 10 9 8 8
15 96 12 14 12 10 9
60 18 15 18 12 10
144 21 27 15 12
35 216 20 15
210 30 18
240 20
30
45
360
MATHEMATICA
Table[Length[Select[Rest[Divisors[n]], IntegerQ[PrimeOmega[n]/PrimeOmega[#]]&]], {n, 100}]
PROG
(PARI) a(n) = my(bn=bigomega(n)); sumdiv(n, d, if (d>1, !(bn % bigomega(d)))); \\ Michel Marcus, Aug 18 2021
(Python)
from sympy import divisors, primeomega
def a(n):
bigomegan = primeomega(n)
return sum(bigomegan%primeomega(d) == 0 for d in divisors(n)[1:])
print([a(n) for n in range(1, 88)]) # Michael S. Branicky, Aug 18 2021
(Python)
from sympy import factorint, divisors
from sympy.utilities.iterables import multiset_combinations
def A347042(n):
fs = factorint(n, multiple=True)
return sum(len(list(multiset_combinations(fs, d))) for d in divisors(len(fs), generator=True)) # Chai Wah Wu, Aug 21 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Aug 17 2021
STATUS
approved