login
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
OFFSET
1,1
COMMENTS
A subsequence of A112041.
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
Sequence in context: A024016 A348583 A349871 * A168307 A323566 A063011
KEYWORD
nonn
AUTHOR
Pierre CAMI, Aug 26 2005
STATUS
approved