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A092474
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a(n) is the first term in a sequence of primes such that a(n)+4m^2 is also prime for m = 1 to n.
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1
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3, 3, 7, 7, 7, 7, 37, 37, 163, 163, 163, 163, 163, 163, 163, 163, 163, 163, 163
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OFFSET
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1,1
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COMMENTS
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a(1) starts sequence A023200; a(2) starts sequence A049492. (I've searched up to 2000000 but haven't yet found the terms from a(20) onward.)
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LINKS
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EXAMPLE
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a(5) = 7.
7+4(1^2) = 7+4(1) = 7+4 = 11 which is prime.
7+4(2^2) = 7+4(4) = 7+16 = 23 which is prime.
7+4(3^2) = 7+4(9) = 7+36 = 43 which is prime.
7+4(4^2) = 7+4(16) = 7+64 = 71 which is prime.
7+4(5^2) = 7+4(25) = 7+100 = 107 which is prime.
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MATHEMATICA
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Flatten[Table[Select[Prime[Range[100]], And@@PrimeQ[Table[#+4n^2, {n, i}]]&, 1], {i, 19}]] (* Harvey P. Dale, Oct 04 2012 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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