login
This site is supported by donations to The OEIS Foundation.
Logo

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A085343 Number of primes between sigma[n] and phi[n]. 1
0, 2, 1, 3, 1, 4, 1, 4, 3, 5, 1, 7, 1, 6, 5, 7, 1, 9, 1, 9, 6, 7, 1, 13, 3, 8, 5, 11, 1, 16, 1, 12, 7, 10, 6, 19, 1, 10, 7, 18, 1, 19, 1, 15, 12, 12, 1, 24, 3, 16, 9, 16, 1, 23, 8, 21, 11, 15, 1, 33, 1, 14, 16, 20, 8, 26, 1, 19, 10, 25, 1, 35, 1, 19, 18, 23, 7, 30, 1, 31, 14, 18, 1, 39, 10, 19 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

FORMULA

a(n)=Pi[sigma(n)]-Pi[phi(n)]=-A000720[A000203(n)]-A000720[A000010(n)]

EXAMPLE

n=12: sigma(12)=28, phi(n)=4, Pi(28)-Pi(4)=9-2=7

CROSSREFS

Cf. A000720, A000010, A000203, A070803, A070804, A085341-A085347.

Sequence in context: A029234 A102613 A097019 * A049077 A180184 A077609

Adjacent sequences:  A085340 A085341 A085342 * A085344 A085345 A085346

KEYWORD

nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu), Jul 10 2003

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified February 15 12:25 EST 2012. Contains 205786 sequences.