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A126960 Primes p such that (3p)^2 + 2 is prime. 1
3, 5, 7, 11, 13, 19, 37, 41, 73, 79, 83, 101, 103, 107, 139, 149, 151, 167, 191, 227, 233, 251, 269, 311, 337, 443, 457, 479, 499, 503, 521, 541, 601, 613, 647, 673, 761, 811, 829, 863, 877, 883, 887, 907, 919, 941, 983, 997 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A generalization of this would be primes p such that (kp)^2+2 is prime. Then k=3 is the only solution. This follows from the fact that k of the form 3m-1 or 3m+1 will give 9m^2 + 6m + 1 + 2, a multiple of 3.

REFERENCES

Garath A. Jones and Mary Jones, Elementary Number Theory, Springer - Verlag London, 1998; p. 35, Exercise 2.17.

LINKS

Table of n, a(n) for n=1..48.

MATHEMATICA

lst={}; Do[p=Prime@n; If[PrimeQ@((3*p)^2+2), AppendTo[lst, p]], {n, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 11 2009 *)

PROG

(PARI) g(n) = forprime(x=0, n, y=9*x^2+2; if(isprime(y), print1(x", ")))

(MAGMA) [ p: p in PrimesUpTo(1000) | IsPrime((3*p)^2+2)] // Vincenzo Librandi, Jan 29 2011

CROSSREFS

Sequence in context: A078425 A020587 A249077 * A119753 A169969 A291175

Adjacent sequences:  A126957 A126958 A126959 * A126961 A126962 A126963

KEYWORD

easy,nonn

AUTHOR

Cino Hilliard, Mar 19 2007

EXTENSIONS

Entries confirmed by Zak Seidov, Mar 19 2007

STATUS

approved

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Last modified September 18 12:39 EDT 2019. Contains 327170 sequences. (Running on oeis4.)