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A227178 Numbers n such that p = n^2 + 1 is prime, as are p-6 and p+6. 1

%I

%S 4,6,16,36,74,116,176,184,654,1276,1314,1394,1524,1546,1686,2676,3074,

%T 3196,3314,3504,3534,3624,3884,4026,4034,4384,4414,4786,5486,5566,

%U 5874,5996,6434,6984,7404,7466,7536,7596,8304,8894,9386,10086,11056,11204,12386

%N Numbers n such that p = n^2 + 1 is prime, as are p-6 and p+6.

%H K. D. Bajpai, <a href="/A227178/b227178.txt">Table of n, a(n) for n = 1..1013</a>

%e a(1)=4 : 4^2+1=17. 17+6=23 and 17-6=11. 11, 17 and 23 are primes.

%p with(StringTools): K := proc(x) local a,b; a:=(x^2+1); if (isprime(a)and isprime(a+6) and isprime(a-6) ) then RETURN (x) fi: end: seq(K(x), x=1..50000); # _K. D. Bajpai_, Jul 03 2013

%p K:=proc()local x,a,b,c; c:=1; for x from 1 to 1000000 do; a:=(x^2+1);if (isprime(a)and isprime(a+6) and isprime(a-6))then lprint(c,x); c:=c+1;fi; od; end: K(); # _K. D. Bajpai_, Jul 03 2013

%o (PARI) is(n)=isprime(n^2-5) && isprime(n^2+1) && isprime(n^2+7) \\ _Charles R Greathouse IV_, Jun 13 2017

%K nonn,easy

%O 1,1

%A _K. D. Bajpai_, Jul 03 2013

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Last modified December 4 02:18 EST 2020. Contains 338921 sequences. (Running on oeis4.)