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%I #11 Sep 08 2022 08:45:48
%S 1,1,1,1,1,0,1,1,1,1,0,1,0,1,1,0,1,1,1,0,0,1,1,0,1,0,0,1,1,1,0,1,1,0,
%T 0,0,0,1,1,1,0,1,1,1,1,0,1,0,1,0,0,1,1,0,0,0,0,1,1,1,0,0,0,1,1,0,1,0,
%U 0,1,0,1,0,1,1,0,1,1,0,1,0,1,0,1,1,0,1,0,0,0,0,0,1,1,1,0,0,1,1,1,0,0,1,0,0
%N a(n) = 1 iff 6n-1 is prime.
%H Vincenzo Librandi, <a href="/A167020/b167020.txt">Table of n, a(n) for n = 1..5000</a>
%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%e a(5) = 1 because 6*5-1 is prime, a(6) = 0 since 6*6-1 is composite.
%t Table[If[PrimeQ[6 n - 1], 1, 0], {n, 100}] (* _Vincenzo Librandi_, Jan 19 2019 *)
%o (PARI) a(n) = isprime(6*n-1); \\ _Michel Marcus_, Jan 19 2019
%o (Magma) [IsPrime(6*n-1) select 1 else 0: n in[1..100]]; // _Vincenzo Librandi_, Jan 19 2019
%Y Cf. A024898, A167021.
%K nonn
%O 1,1
%A _Washington Bomfim_, Oct 27 2009