A224991 - OEIS

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A224991

Primes p such that q=2*p^2-1, r=2*p*q-1 and 2*p*r-1 are also prime.

181, 32341, 52021, 96907, 97171, 100981, 109507, 192601, 194671, 238237, 280627, 304651, 320911, 418321, 449971, 547537, 579961, 626191, 668611, 767857, 769807, 771091, 806107, 885097, 954157, 991381, 993247, 1028047, 1075357, 1259677, 1285021, 1368727, 1414837, 1415191, 1425007, 1449841

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Subsequence of A224990, and more elementary version of A224626.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..500

MATHEMATICA

qr[p_]:=Module[{q=2p^2-1, r}, r=2p*q-1; {q, r, 2p*r-1}]; Select[Prime[ Range[ 120000]], AllTrue[qr[#], PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Apr 10 2015 *)

PROG

(PARI) forprime(p=1, 2e6, isprime(q=2*p^2-1)&&isprime(r=2*p*q-1)&&isprime(2*p*r-1)&&print1(p", "))

CROSSREFS

Cf. A224626, A224990.

Sequence in context: A226714 A083979 A179408 * A189342 A189778 A322904

Adjacent sequences: A224988 A224989 A224990 * A224992 A224993 A224994

KEYWORD

nonn

AUTHOR

M. F. Hasler, Apr 22 2013

STATUS

approved