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A335139
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a(n) = (prime(n + 1) +- k) / 2 where k is the smallest possible odd number such that a(n) is prime and a(n + 1) >= a(n).
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0
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2, 3, 3, 5, 7, 7, 11, 11, 13, 17, 19, 19, 23, 23, 29, 29, 31, 31, 37, 37, 41, 41, 43, 47, 53, 53, 53, 53, 59, 61, 67, 67, 71, 73, 73, 79, 83, 83, 89, 89, 89, 97, 97, 97, 101, 107, 113, 113, 113, 113, 113, 127, 127, 127, 131, 137, 137, 139, 139, 139, 149
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OFFSET
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1,1
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COMMENTS
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The sequence of k's begins {1, 1, -1, -1, 1, -3, 3, -1, -3, 3, 1, -3, 3, -1, ...}. I conjecture that the partial sums of the k's sequence change sign infinitely often and that their absolute value is less than the square root of n.
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LINKS
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PROG
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(PARI) forprime(n = 3, 300, forstep(j = 1, 999, 2, a = (n + j)/2; b =(n - j)/2; if(isprime(a), print1(a", "); break); if(isprime(b), print1(b", "); break)))
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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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