Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A121494
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A121494 Composite numbers n such that tau(n) = tau(2n+1). +0
1
4, 10, 27, 34, 38, 46, 55, 57, 62, 76, 77, 91, 93, 106, 118, 123, 129, 133, 136, 143, 145, 159, 161, 177, 185, 201, 203, 205, 206, 212, 213, 218, 226, 232, 235, 259, 267, 291, 295, 297, 298, 305, 310, 314, 322, 327, 334, 335, 339, 343, 357, 358, 365, 370, 377 (list; graph; listen)
OFFSET

0,1

COMMENT

Composite terms of A074821, while prime terms of A074821 are Sophie Germain primes A005384.

EXAMPLE

10 is OK since both 10 and 2*10+1=21 have 4 divisors;

{1,2,5,10} and {1,3,7,21}.

CROSSREFS

Cf. A005384, A074821.

Sequence in context: A087222 A130583 A105999 this_sequence A122744 A077923 A052982

Adjacent sequences: A121491 A121492 A121493 this_sequence A121495 A121496 A121497

KEYWORD

nonn

AUTHOR

Zak Seidov (zakseidov(AT)yahoo.com), Aug 03 2006

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 25 14:49 EST 2009. Contains 167514 sequences.


AT&T Labs Research