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A321864
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a(n) = A321859(prime(n)).
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15
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-1, 0, 1, 1, 0, 1, 2, 3, 2, 1, 2, 1, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 3, 2, 3, 2, 1, 2, 1, 2, 3, 2, 3, 2, 1, 0, 1, 0, 1, 2, 3, 2, 1, 2, 3, 4, 3, 4, 5, 4, 3, 4, 5, 6, 7, 8, 7, 6, 5, 4, 5, 6, 5, 6, 5, 4, 5, 4, 5, 4, 5, 6, 5, 4, 5, 6, 5, 4
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OFFSET
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1,7
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COMMENTS
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Among the first 10000 terms there are only 13 negative ones, with the earliest one (besides a(1)) being a(5006) = -1.
Please see the comment in A321856 describing "Chebyshev's bias" in the general case.
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LINKS
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FORMULA
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a(n) = -Sum_{primes p<=n} Legendre(prime(i),7) = -Sum_{primes p<=n} Kronecker(-7,prime(i)) = -Sum_{i=1..n} A175629(prime(i)).
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EXAMPLE
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prime(25) = 97. Among the primes <= 97, there are 10 ones congruent to 1, 2, 4 modulo 7 and 14 ones congruent to 3, 5, 6 modulo 7, so a(25) = 14 - 10 = 4.
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PROG
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(PARI) a(n) = -sum(i=1, n, kronecker(-7, prime(i)))
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CROSSREFS
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Let d be a fundamental discriminant.
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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