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Numbers n such that p=6*n+1, q=6*p+1 and r=6*q+1 are primes.
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%I #11 Oct 17 2015 17:41:18

%S 10,25,55,61,101,125,156,220,221,381,391,465,475,495,576,810,891,901,

%T 975,1060,1145,1396,1430,1630,1650,1726,1795,1811,1881,1885,1915,2196,

%U 2265,2335,2391,2405,2456,2536,2575,2636,2651,2820,2911,2915,2951,2965,3051,3211,3245,3335

%N Numbers n such that p=6*n+1, q=6*p+1 and r=6*q+1 are primes.

%C Subsequence of A263309 (and as such also of A024899).

%p isA263310 := proc(n)

%p return isprime(6*n+1) and isprime(36*n+7) and isprime(216*n+43) ;

%p end proc:

%p for n from 1 to 3000 do

%p if isA263310(n) then

%p printf("%d,",n);

%p end if;

%p end do: # _R. J. Mathar_, Oct 17 2015

%t Select[Range[10000],PrimeQ[p=6*#+1]&& PrimeQ[q=6*p+1]&& PrimeQ[r=6*q+1]&]

%o (PARI) for(n=1, 1e4, if(isprime(p=6*n+1)&&isprime(q=6*p+1)&&isprime(6*q+1), print1(n", "))) \\ _Altug Alkan_, Oct 17 2015

%Y Cf. A024899, A263309.

%K nonn

%O 1,1

%A _Zak Seidov_, Oct 13 2015