login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A115272 Primes p such that p + 2, 18*p^2 + 1, and 18*(p+2)^2 + 1 are all primes. 0
29, 107, 431, 1487, 1607, 2141, 5501, 10139, 10271, 17579, 22481, 23057, 27479, 32369, 36341, 36929, 38447, 55931, 57527, 69827, 75539, 78539, 79691, 81047, 81971, 84179, 86027, 89561, 93761, 102059, 112571, 113147, 118799, 119687 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..34.

EXAMPLE

a(1)=29 because 31, 18*29^2 + 1 = 15139, and 18*31^2 + 1 = 17299 are all primes.

PROG

(Magma) [p: p in PrimesUpTo(200000)| IsPrime(p+2) and IsPrime(18*p^2+1) and IsPrime(18*(p+2)^2+1)] // Vincenzo Librandi, Nov 13 2010

CROSSREFS

Cf. A089001 (Numbers n such that 2*n^2 + 1 is prime),

A090612 (Numbers k such that the k-th prime is of the form 2*k^2+1),

A090698 (Primes of the form 2*n^2+1),

A113541 (Numbers n such that 18*n^2+1 is a multiple of 19).

Sequence in context: A233049 A233050 A142176 * A138716 A276776 A142194

Adjacent sequences: A115269 A115270 A115271 * A115273 A115274 A115275

KEYWORD

nonn

AUTHOR

Zak Seidov, Jan 19 2006

EXTENSIONS

More terms from Vincenzo Librandi, Mar 27 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 2 07:55 EST 2022. Contains 358493 sequences. (Running on oeis4.)