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A227178
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Numbers k such that p = k^2 + 1 is prime, as are p-6 and p+6.
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1
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4, 6, 16, 36, 74, 116, 176, 184, 654, 1276, 1314, 1394, 1524, 1546, 1686, 2676, 3074, 3196, 3314, 3504, 3534, 3624, 3884, 4026, 4034, 4384, 4414, 4786, 5486, 5566, 5874, 5996, 6434, 6984, 7404, 7466, 7536, 7596, 8304, 8894, 9386, 10086, 11056, 11204, 12386
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(1)=4: 4^2 + 1 = 17, 17 + 6 = 23 and 17 - 6 = 11; 11, 17 and 23 are primes.
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MAPLE
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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
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
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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