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A112042 Numbers k such that 1*k + 1, 3*k + 1, 9*k + 1, 27*k + 1, 81*k + 1 are all primes. 2
60, 760, 2440, 5800, 8680, 17350, 21840, 27010, 40030, 84060, 108010, 109890, 131110, 222940, 277750, 309120, 313030, 334170, 346140, 348660, 356500, 358330, 387160, 419230, 470880, 553410, 578820, 604030, 683340, 729820, 799890, 801630 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A subsequence of A112041.

LINKS

Table of n, a(n) for n=1..32.

MATHEMATICA

prQ[n_]:=Module[{ns=n*3^Range[0, 4]+1}, And@@PrimeQ[ns]]; Select[Range[ 810000], prQ] (* Harvey P. Dale, Jul 01 2012 *)

PROG

(MAGMA) [n: n in [1..1000000] |IsPrime(n+1) and IsPrime(3*n+1) and IsPrime(9*n+1) and IsPrime(27*n+1)and IsPrime(81*n+1)] // Vincenzo Librandi, Nov 13 2010

CROSSREFS

Cf. A112041, A112043.

Sequence in context: A034865 A138409 A024016 * A168307 A323566 A063011

Adjacent sequences:  A112039 A112040 A112041 * A112043 A112044 A112045

KEYWORD

nonn

AUTHOR

Pierre CAMI, Aug 26 2005

STATUS

approved

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Last modified November 14 17:24 EST 2019. Contains 329126 sequences. (Running on oeis4.)