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A038880
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Primes p such that 10 is not a square mod p.
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4
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7, 11, 17, 19, 23, 29, 47, 59, 61, 73, 97, 101, 103, 109, 113, 127, 131, 137, 139, 149, 167, 179, 181, 193, 211, 223, 229, 233, 251, 257, 263, 269, 313, 331, 337, 349, 353, 367, 379, 383, 389, 419, 421, 433, 457, 461, 463, 487, 491, 499, 503, 509, 541, 571
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OFFSET
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1,1
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COMMENTS
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Inert rational primes in the field Q(sqrt(10)). - N. J. A. Sloane, Dec 26 2017
Also primes p such that p divides 5^(p-1)/2 + 2^(p-1)/2. - Cino Hilliard, Sep 06 2004
Primes p such that p-1 divided by the number of the digits of the period of 1/p results in an odd number. - Davide Rotondo, Apr 28 2024
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LINKS
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FORMULA
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MATHEMATICA
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Select[ Prime@Range[2, 105], JacobiSymbol[10, # ] == -1 &] (* Robert G. Wilson v, Dec 15 2005 *)
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PROG
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(PARI) list(lim)=my(v=List()); forprime(p=7, lim, if(kronecker(10, p)<0, listput(v, p))); Vec(v) \\ Charles R Greathouse IV, Mar 18 2018
(Python)
from sympy import isprime, jacobi_symbol
def ok(n): return n%2 == 1 and isprime(n) and jacobi_symbol(10, n) == -1
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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