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A304875
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Least prime p2 > p1 such that n^2 = (p1 + p2)/2 and p1 is prime.
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5
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5, 11, 19, 31, 41, 61, 67, 83, 103, 139, 149, 181, 199, 227, 271, 307, 331, 373, 421, 443, 547, 571, 631, 631, 691, 739, 811, 853, 919, 1039, 1039, 1091, 1249, 1237, 1301, 1447, 1459, 1531, 1621, 1693, 1787, 1867
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OFFSET
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2,1
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COMMENTS
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Each square > 1 can be written as the average of 2 primes p1 < p2. a(n) gives the least prime p2 such that n^2 = (p1 + p2) / 2. The corresponding p1 is provided in A304874.
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LINKS
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FORMULA
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EXAMPLE
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a(2) = 5 because 2^2 = 4 = (3 + 5)/2,
a(7) = 61 because 7^2 = 49 = (37 + 61)/2 and p2 = 53 or p2 = 59 don't lead to a prime p1.
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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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