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A102342 Numbers k such that 10k + 7 is prime. 11

%I

%S 0,1,3,4,6,9,10,12,13,15,16,19,22,25,27,30,31,33,34,36,39,45,46,48,54,

%T 55,57,58,60,61,64,67,72,75,78,79,82,85,87,88,90,93,94,96,97,99,108,

%U 109,111,118,121,123,127,129,130,132,136,142,144,148,156,159,160,162,163

%N Numbers k such that 10k + 7 is prime.

%C Solutions of the equation (10*k+7)'=1, where k' is the arithmetic derivative of k. - _Paolo P. Lava_, Nov 15 2012

%e 10*1 + 7 = 17 (prime);

%e 10*48 + 7 = 487 (prime);

%e 10*99 + 7 = 997 (prime).

%t Select[Range[0, 170], PrimeQ[10# + 7] &] (* _Ray Chandler_, Nov 07 2006 *)

%o (MAGMA) [n: n in [0..3000]| IsPrime(10*n+7)]; // _Vincenzo Librandi_, Apr 06 2011

%o (PARI) is(n)=isprime(10*n+7) \\ _Charles R Greathouse IV_, Feb 17 2017

%Y Cf. A030432, A049509.

%K nonn

%O 1,3

%A _Parthasarathy Nambi_, Feb 20 2005

%E Edited and extended by _Ray Chandler_, Nov 07 2006

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Last modified May 18 10:19 EDT 2021. Contains 343995 sequences. (Running on oeis4.)