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!)
A164623 Primes p such that p*(p-1)/2-5 and p*(p-1)/2+5 are also prime numbers. 1
13, 157, 673, 1069, 1117, 1153, 1213, 1597, 2029, 2089, 2437, 2713, 2833, 3613, 4057, 4909, 5653, 6337, 6529, 7549, 7993, 8053, 9613, 10789, 11497, 11689, 12073, 12373, 13309, 13669, 13789, 14173, 15289, 15937, 16249, 18097, 18637, 19249, 19993 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes A000040(k) such that A008837(k)+-5 are also prime numbers.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

EXAMPLE

13 is in the sequence because 13*6-5=73 and 13*6+5=83 are both prime.

MATHEMATICA

Select[Prime[Range[2300]], PrimeQ[# (# - 1)/2 - 5] && PrimeQ[# (# - 1)/2 + 5] &]

PROG

(PARI) forprime(p=2, 10^6, my(b=binomial(p, 2)); if(isprime(b-5)&isprime(b+5), print1(p, ", "))); /* Joerg Arndt, Apr 10 2013 */

CROSSREFS

Cf. A008846, A020882, A068228, A068229, A082539, A086519, A107159, A158708, A139494, A164620, A164621, A164622, A023203.

Sequence in context: A140020 A130868 A154414 * A072841 A244206 A159499

Adjacent sequences:  A164620 A164621 A164622 * A164624 A164625 A164626

KEYWORD

nonn,easy

AUTHOR

Vladimir Joseph Stephan Orlovsky, Aug 17 2009

EXTENSIONS

Edited by R. J. Mathar, Aug 20 2009

Mathematica code adapted to the definition by Bruno Berselli, Apr 10 2013

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 April 5 19:56 EDT 2020. Contains 333260 sequences. (Running on oeis4.)