Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A144774
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A144774 Number of positive integers k less than n such that rad(k) < rad(n). +0
3
0, 1, 2, 1, 4, 5, 6, 1, 4, 9, 10, 7, 12, 13, 14, 1, 16, 8, 18, 12, 20, 21, 22, 8, 7, 25, 5, 19, 28, 29, 30, 1, 32, 33, 34, 11, 36, 37, 38, 17, 40, 41, 42, 28, 24, 45, 46, 11, 17, 19, 50, 35, 52, 11, 54, 26, 56, 57, 58, 40, 60, 61, 33, 1, 64, 65, 66, 46, 68, 69, 70, 12, 72, 73, 31, 52, 76 (list; graph; listen)
OFFSET

1,3

COMMENT

a(n) = n - 1 if n is a product of distinct primes, since these have rad(n) = n.

EXAMPLE

rad(1) = 1 and rad(2) = 2, so a(2) = 1.

rad(4) is also 2, so a(4) = 1.

rad(12) = 6. The integers k less than 12 for which rad(k) < 6 are 1, 2, 3, 4, 5, 8 and 9. a(12) = 7.

CROSSREFS

Cf. A007947

Sequence in context: A165046 A047949 A075423 this_sequence A074720 A058359 A110332

Adjacent sequences: A144771 A144772 A144773 this_sequence A144775 A144776 A144777

KEYWORD

easy,nonn

AUTHOR

Reikku Kulon (reikku(AT)gmail.com), Sep 21 2008

page 1

Search completed in 0.002 seconds

Lookup | Welcome | Find friends | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
More pages | Superseeker | Maintained by N. J. A. Sloane (njas@research.att.com)

Last modified December 16 17:18 EST 2009. Contains 170825 sequences.


AT&T Labs Research