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%I A367970 #29 Dec 18 2023 13:06:16
%S A367970 2,1,2,2,4,1,2,1,4,2,6,1,2,1,2,3,12,2,2,1,2,3,4,2,2,1,2,2,10,1,2,4,2,
%T A367970 6,4,1,8,1,6,2,4,1,2,3,8,2,4,1,2,1,4,2,4,1,12,1,2,5,4,2,6,1,2,2,4,1,6,
%U A367970 3,2,2,6,5,18,4,2,2,6,3,6,1,2,2,28,1,6
%N A367970 Least k such that 5*n*k+1 is a prime.
%H A367970 Robert Price, <a href="/A367970/b367970.txt">Table of n, a(n) for n = 1..5000</a>
%t A367970 A367970 = {};
%t A367970 Do[k=1; While[!PrimeQ[5 n k+1], k++]; AppendTo[A367970 ,k], {n,85}];
%t A367970 A367970
%o A367970 (PARI) a(n) = my(k=1); while (!isprime(5*n*k+1), k++); k; \\ _Michel Marcus_, Dec 17 2023
%Y A367970 Cf. A016014, A024894.
%Y A367970 A070849 lists the corresponding primes.
%K A367970 nonn
%O A367970 1,1
%A A367970 _Robert Price_, Dec 17 2023

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