OFFSET
1,3
COMMENTS
A logarithmic plot of this sequence shows an unusual banded structure.
LINKS
T. D. Noe, Table of n, a(n) for n=1..10000
T. D. Noe, Plot of A092694
FORMULA
a(1) = 1, a(n) = phi(n) * a(phi(n))
EXAMPLE
a(100) = 40960 because the iterations of phi (40, 16, 8, 4, 2, 1) have a product of 40960.
MATHEMATICA
nMax=100; a=Table[1, {nMax}]; Do[e=EulerPhi[n]; a[[n]]=e*a[[e]], {n, 2, nMax}]; a
PROG
(Haskell)
a092694 n = snd $ until ((== 1) . fst) f (a000010 n, 1) where
f (x, p) = (a000010 x, p * x)
-- Reinhard Zumkeller, Jan 30 2014
(Python)
from sympy import totient
from math import prod
def f(n):
m = n
while m > 1:
m = totient(m)
yield m
def A092694(n): return prod(f(n)) # Chai Wah Wu, Nov 14 2021
CROSSREFS
KEYWORD
nonn,look
AUTHOR
T. D. Noe, Mar 04 2004
STATUS
approved