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A023228
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Numbers k such that k and 8*k + 1 are both prime.
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9
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2, 5, 11, 17, 29, 71, 101, 107, 131, 137, 149, 179, 239, 269, 347, 401, 431, 449, 479, 491, 509, 557, 599, 617, 659, 677, 761, 809, 821, 857, 929, 941, 947, 977, 1151, 1187, 1229, 1289, 1307, 1361, 1367, 1409, 1487, 1559, 1571, 1601, 1619, 1667, 1697, 1811, 1871
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OFFSET
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1,1
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LINKS
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FORMULA
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Sum_{n>=1} 1/a(n) is in the interval (1.151956749, 1.4207187) (Wagstaff, 2021). - Amiram Eldar, Nov 04 2021
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MATHEMATICA
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PROG
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(Magma) [ p: p in PrimesUpTo(1900) | IsPrime(8*p+1) ]; // Klaus Brockhaus, Dec 21 2008
(PARI) list(lim)=my(v=List()); forprime(p=2, lim, if(isprime(8*p+1), listput(v, p))); Vec(v) \\ Charles R Greathouse IV, Oct 20 2021
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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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