login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A143144 A positive integer n is included if there is one and only one prime p where j < p < k, where j is the largest divisor of n that is <= sqrt(n) and k = the smallest divisor of n that is >= sqrt(n). 3
3, 8, 10, 18, 21, 24, 28, 40, 45, 48, 50, 54, 55, 60, 66, 84, 91, 96, 104, 108, 117, 120, 130, 154, 165, 168, 176, 180, 187, 192, 204, 234, 247, 252, 266, 270, 285, 288, 304, 340, 357, 360, 374, 378, 391, 396, 414, 456, 475, 480, 494, 500, 504, 513, 520, 525 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

The divisors of 40 are 1,2,4,5,8,10,20,40. The two middle divisors are 5 and 8. Between 5 and 8 (and not including 5 and 8) there is exactly one prime (7). So 40 is included in the sequence.

CROSSREFS

Cf. A143143, A143145.

Sequence in context: A341938 A341939 A244353 * A261929 A020488 A064435

Adjacent sequences:  A143141 A143142 A143143 * A143145 A143146 A143147

KEYWORD

nonn

AUTHOR

Leroy Quet, Jul 27 2008

EXTENSIONS

a(9)-a(56) from Donovan Johnson, Sep 27 2008

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 19 12:45 EDT 2021. Contains 345129 sequences. (Running on oeis4.)