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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A171995 Twin natural nonprimes with nonprime number of prime factors. 0
1, 625, 1715, 1925, 2125, 2875, 2975, 3575, 3773, 4165, 4225, 4235, 4625, 5125, 5375, 5425, 5635, 5831, 5875, 5915, 6517, 6625, 7007, 7225, 7315, 7375, 7595, 7625, 7735, 7889, 7975, 8075, 8225, 8281, 8855, 8875, 9025, 9425, 9775, 9875, 10045, 10075 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Intersection of A171697 and A167175. [From R. J. Mathar, Mar 29 2010]

LINKS

Table of n, a(n) for n=1..42.

EXAMPLE

a(1)=1(without prime factors), a(2)=625(=5*5*5*5), a(3)=1715(=5*7*7*7).

PROG

(PARI) isA171995(n)=n>0&!isprime(n)&((n%6==1&!isprime(n-2))|(n%6==5&!isprime(n+2)))&!isprime(bigomega(n))

CROSSREFS

Cf. A171697.

Sequence in context: A186483 A043352 A223183 * A262798 A250431 A046755

Adjacent sequences:  A171992 A171993 A171994 * A171996 A171997 A171998

KEYWORD

nonn,less

AUTHOR

Juri-Stepan Gerasimov, Jan 21 2010

EXTENSIONS

Edited and extended by Charles R Greathouse IV, Mar 29 2010

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 March 20 15:43 EDT 2019. Contains 321345 sequences. (Running on oeis4.)