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A175283 Numbers k with the property that k and k^2 + 3k+9 are primes. 1

%I

%S 2,7,11,17,23,29,31,37,43,73,101,107,127,163,179,197,239,277,281,317,

%T 331,359,367,421,457,463,487,541,569,613,617,619,661,709,739,773,787,

%U 809,823,877,941,947,953,991,1019,1031,1033,1039,1051,1087,1163,1187

%N Numbers k with the property that k and k^2 + 3k+9 are primes.

%C Or, primes in A175282.

%t Select[Prime[Range[400]],PrimeQ[ #^2+3*#+9]&]

%o (MAGMA) [ n: n in [0..1250] | IsPrime(n) and IsPrime(n^2+3*n+9)] // _Vincenzo Librandi_, Jan 30 2011

%Y Cf. A005471, A175281, A175282.

%K nonn

%O 1,1

%A _Zak Seidov_, Mar 21 2010

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Last modified July 8 08:08 EDT 2020. Contains 335520 sequences. (Running on oeis4.)