OFFSET
1,2
LINKS
Jean-François Alcover, Table of n, a(n) for n = 1..10000
MATHEMATICA
smooth3Q[n_] := n/2^IntegerExponent[n, 2]/3^IntegerExponent[n, 3] == 1;
Select[Range[1000], PrimePowerQ[#] || smooth3Q[#]&] (* Jean-François Alcover, Oct 14 2021 *)
PROG
(Python)
from sympy import integer_log, primepi, integer_nthroot
def A081061(n):
def f(x): return int(n+x-1+(a:=x.bit_length())+(b:=integer_log(x, 3)[0])-sum((x//3**i).bit_length() for i in range(b+1))-sum(primepi(integer_nthroot(x, k)[0]) for k in range(1, a)))
m, k = n, f(n)
while m != k: m, k = k, f(k)
return m # Chai Wah Wu, Sep 16 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Mar 04 2003
STATUS
approved