Intended for: September 13, 2011
Timetable
- First draft entered by Charles R Greathouse IV on July 13, 2011 ✓
- Draft reviewed by Alonso del Arte on July 13, 2011 ✓
- Draft approved by Alonso del Arte on August 11, 2011 ✓
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A070243:
Card{ k | φ (k) ≤ n }, n ≥ 1 |
.
-
{ 2, 5, 5, 9, 9, 13, 13, 18, 18, 20, 20, 26, 26, 26, 26, 32, 32, 36, 36, 41, 41, 43, 43, 53, ... }
This sequence counts the number of positive integers
such that
, where
is
Euler’s totient function. It has
natural density , so in some sense the values of
are on average not much less than
.
Note that
a (n) − a (n − 1) = Card{ k | φ (k) = n }, n ≥ 1, |
(see
A014197) and thus
.