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A024912 Numbers n such that 10n + 1 is prime. 19

%I

%S 1,3,4,6,7,10,13,15,18,19,21,24,25,27,28,31,33,40,42,43,46,49,52,54,

%T 57,60,63,64,66,69,70,75,76,81,82,88,91,94,97,99,102,103,105,106,109,

%U 115,117,118,120,123,129,130,132,136,138,145,147,148,151,153,157,160,162

%N Numbers n such that 10n + 1 is prime.

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

%H T. D. Noe, <a href="/A024912/b024912.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = (A081759(n)+1)/2.

%t Select[Range[170], PrimeQ[10# + 1] &] (* _Ray Chandler_, Dec 06 2006 *)

%o (MAGMA) [n: n in [1..1000] |IsPrime(10*n+1)] // _Vincenzo Librandi_, Nov 19 2010]

%o (PARI) is(n)=isprime(10*n+1) \\ _Charles R Greathouse IV_, Jul 02 2013

%Y Cf. A030430, A049511, A081759.

%K nonn,easy

%O 1,2

%A _Clark Kimberling_

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Last modified May 8 18:28 EDT 2021. Contains 343666 sequences. (Running on oeis4.)