Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A002246
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A002246 Given a rational number r = p/q, where q>0, (p,q)=1, define its height to be max{|p|,q}; then a(n) = number of rational numbers of height n. +0
4
3, 4, 8, 8, 16, 8, 24, 16, 24, 16, 40, 16, 48, 24, 32, 32, 64, 24, 72, 32, 48, 40, 88, 32, 80, 48, 72, 48, 112, 32, 120, 64, 80, 64, 96, 48, 144, 72, 96, 64, 160, 48, 168, 80, 96, 88, 184, 64, 168, 80, 128, 96, 208, 72, 160, 96, 144, 112, 232, 64, 240, 120, 144, 128, 192, 80, 264 (list; graph; listen)
OFFSET

1,1

COMMENT

The old entry with this sequence number was a duplicate of A008831.

a(n) is also the number of integers prime to n in the interval [n+1, 5n-1]. [From W. Bomfim (webonfim(AT)bol.com.br), Oct 10 2009]

REFERENCES

M. N. Huxley, Area, Lattice Points and Exponential Sums, Oxford, 1996; p. 7.

FORMULA

a(1) = 3; thereafter a(n) = 4*phi(n) = 4*A000010(n).

EXAMPLE

The three rational numbers of height 1 are 0, 1 and -1.

CROSSREFS

Cf. A000010, A097080.

Sequence in context: A034772 A065309 A097689 this_sequence A030014 A047968 A125219

Adjacent sequences: A002243 A002244 A002245 this_sequence A002247 A002248 A002249

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Nov 02 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 November 24 23:16 EST 2009. Contains 167481 sequences.


AT&T Labs Research