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%I #30 Feb 04 2024 01:19:27
%S 2,3,6,8,9,11,14,15,18,20,23,24,27,35,36,38,39,41,42,44,45,48,50,51,
%T 57,60,62,66,71,72,74,77,81,83,84,86,92,93,101,102,104,105,107,111,
%U 113,123,125,126,128,129,132,140,141,143,144,146,149,150,155,156,158,161,162
%N Numbers n such that 10n - 1 is prime.
%H Vincenzo Librandi, <a href="/A105042/b105042.txt">Table of n, a(n) for n = 1..1000</a>
%F a(k) = (A030433(k) + 1)/10. - _R. J. Mathar_, Jul 08 2009
%e If n = 2, then 10*n - 1 = 19 (prime).
%e If n = 18, then 10*n - 1 = 179 (prime).
%e If n = 36, then 10*n - 1 = 359 (prime).
%p a:= proc(n) if isprime(10*n-1) then n end if end proc: seq(a(n), n = 1 .. 200); # _Emeric Deutsch_, Aug 02 2009
%t Select[Range[200], PrimeQ[10# - 1] &] (* _Alonso del Arte_, Feb 09 2014 *)
%o (Magma) [n: n in [1..200]| IsPrime(10*n-1)] // _Vincenzo Librandi_, Feb 10 2014
%o (PARI) is(n)=isprime(10*n-1) \\ _Charles R Greathouse IV_, Jun 12 2017
%K nonn,easy
%O 1,1
%A _Parthasarathy Nambi_, Apr 03 2005
%E Extended by _Emeric Deutsch_, Aug 02 2009
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