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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A122001 Number of representations of prime p = prime(n) as 2*(p1-p2)+3*p3 (where p1, p2, p3 are primes less than or equal than p), for which p+2*p2(=2*p1+3*p3) is also a prime. 0
0, 0, 0, 1, 0, 3, 7, 5, 7, 8, 6, 17, 15, 10, 13, 19, 9, 21, 24, 18, 29, 28, 25, 37, 37, 29, 32, 34, 37, 47, 40, 37, 63, 51, 57, 59, 69, 47, 58, 67, 65, 68, 65, 69, 65, 60, 73, 97, 90, 109, 103, 82, 111, 112, 96, 106, 140 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Table of n, a(n) for n=1..57.

EXAMPLE

a(6)=3 because although 13 (the 6th prime) can be expressed as 2*(p1-p2) + 3*p3 in the following ways:

2*( 2 - 3 ) + 3* 5

2*( 3 - 7 ) + 3* 7

2*( 3 - 13 ) + 3* 11

2*( 5 - 3 ) + 3* 3

2*( 7 - 5 ) + 3* 3

2*( 7 - 11 ) + 3* 7

2*( 13 - 11 ) + 3* 3

only for the three of them (first, fourth and fifth) p+2*p2 is also a prime (19, 19, 23, respectively)

CROSSREFS

Cf. A120450, A120451.

Sequence in context: A019638 A116535 A287660 * A161327 A151685 A019809

Adjacent sequences:  A121998 A121999 A122000 * A122002 A122003 A122004

KEYWORD

nonn

AUTHOR

Vassilis Papadimitriou, Sep 11 2006

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 20 08:50 EDT 2018. Contains 313914 sequences. (Running on oeis4.)