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-1, 3, 1, -5, -1, 5, 7, -5, -3, 5, 9, -1, 3, -7, -11, 7, 11, -13, -9, -7, -1, 15, 13, -15, 1, -13, -9, 5, -17, 13, 11, 9, -5, 17, 7, -17, 19, 1, -3, 15, 17, -7, 21, 19, -5, -11, -21, 19, 13, 1, -23, 5, -17, -19, 25, -13, -25, -23, -1, -5, 15, 27, -9, -19, 25, -17, 11, 5, -25, 27, 23, 29, -29, 25
(list;
graph;
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listen;
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internal format)
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OFFSET
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1,2
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LINKS
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EXAMPLE
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Let p be a prime of the form 4k+1 so that p = a^2 + b^2.
We take a odd and such that a = b + 1 (mod 4).
p = 5 = (-1)^2 + 2^2 and -1 = 2 + 1 (mod 4). So a(1) = -1.
p = 13 = 3^2 + 2^2 and 3 = 2 + 1 (mod 4). So a(2) = 3.
p = 17 = 1^2 + 4^2 and 1 = 4 + 1 (mod 4). So a(3) = 1.
p = 29 = 5^2 + 2^2 and -5 = 2 + 1 (mod 4). So a(4) = -5.
(End)
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MATHEMATICA
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PROG
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(PARI) a002172(n) = {my(m, c); if(n<1, 0, c=0; m=0; while(c<n, m++; if(isprime(m)& m%4==1, c++)); -sum(x=0, m-1, kronecker(x^3-x, m)))}
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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