A112042 - OEIS

A112042

Numbers k such that 1*k + 1, 3*k + 1, 9*k + 1, 27*k + 1, 81*k + 1 are all primes.

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

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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: A024016 A348583 A349871 * A168307 A323566 A063011

Adjacent sequences: A112039 A112040 A112041 * A112043 A112044 A112045

KEYWORD

nonn

AUTHOR

Pierre CAMI, Aug 26 2005

STATUS

approved