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%I A056956 #11 Apr 05 2017 20:54:37
%S A056956 1,2,3,6,7,11,13,16,17,18,21,27,32,37,38,46,51,52,58,63,66,73,76,77,
%T A056956 81,83,102,107,112,123,126,128,137,142,143,146,147,151,156,161,168,
%U A056956 181,182,202,213,216,217,237,238,241,247,248,258,261,263,266,268,277,282
%N A056956 Numbers n such that 6n+1 and 6n+5 are both primes.
%C A056956 Note that if prime p>3 then p mod 6 = 1 or 5.
%H A056956 M. F. Hasler, <a href="/A056956/b056956.txt">Table of n, a(n) for n = 1..5000</a>
%F A056956 a(n) = (A023200(n+1)-1)/6 = (A046132(n+1)-5)/6 = A047847(n+1)/3
%F A056956 a(n) = floor(A087679(n+1)/6). - _M. F. Hasler_, Apr 05 2017
%e A056956 a(2)=2 since 6*2+1=13 and 6*2+5=17 are both prime.
%t A056956 Select[Range[300], And @@ PrimeQ /@ ({1, 5} + 6#) &] (* _Ray Chandler_, Jun 29 2008 *)
%o A056956 (PARI) is(n)=isprime(n*6+1)&&isprime(n*6+5) \\ _M. F. Hasler_, Apr 05 2017
%Y A056956 Cf. A002822, A024898, A024899, A059325.
%K A056956 nonn
%O A056956 1,2
%A A056956 _Henry Bottomley_, Jul 18 2000
%E A056956 Edited by _N. J. A. Sloane_, Nov 07 2006

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