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

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A140221 A number n is included if n is coprime to sum{k=1 to n} d(k), where d(k) is the number of divisors of k. 1
1, 2, 3, 7, 9, 10, 11, 12, 13, 14, 17, 19, 23, 25, 27, 28, 29, 31, 32, 34, 35, 37, 41, 43, 45, 49, 50, 51, 52, 53, 54, 56, 58, 59, 61, 62, 65, 67, 69, 71, 73, 75, 77, 79, 81, 82, 83, 84, 86, 87, 88, 89, 92, 93, 94, 95, 97, 98, 101, 103, 107, 109, 111, 113, 115, 117, 119, 122 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

COMMENTS

sum{k=1 to n} d(k) = sum{k=1 to n} floor(n/k) = A006218(n).

CROSSREFS

Cf. A006218, A050226, A140222.

Sequence in context: A053960 A114056 A168222 * A046668 A047533 A060525

Adjacent sequences:  A140218 A140219 A140220 * A140222 A140223 A140224

KEYWORD

nonn

AUTHOR

Leroy Quet May 12 2008

EXTENSIONS

More terms from Max Alekseyev (maxale(AT)gmail.com), May 10 2009

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 17 21:13 EST 2012. Contains 206085 sequences.