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A247874 Lesser of twin primes (p, q=p+2) such that 7 is a square mod p and mod q. 1
29, 137, 197, 281, 419, 617, 641, 809, 1061, 1091, 1229, 1289, 1427, 1481, 1877, 1931, 2129, 2237, 2267, 2381, 2549, 2657, 2687, 2801, 2969, 3329, 3359, 3389, 3527, 3557, 3581, 3917, 4001, 4229, 4337, 4421, 4481, 4649, 4787, 5009, 5657, 5741, 5849, 5879, 6131, 6269, 6299, 6551, 6689, 7307 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Both p and p + 2 are terms in A038878.

All terms are congruent to {1, 25, 27} mod 28.

LINKS

Zak Seidov, Table of n, a(n) for n = 1..1000

EXAMPLE

7+29*1=36=6^2 and 7+31*3=100=10^2 hence 7 is a square mod 29 and mod 31.

MATHEMATICA

Select[Prime[Range[5, 1000]], PrimeQ[# + 2] && JacobiSymbol[7, #] == JacobiSymbol[7, # + 2] == 1 &]

PROG

(PARI) lista(nn) = {forprime(p=2, nn, if (isprime(q=p+2) && issquare(Mod(7, p)) && issquare(Mod(7, q)), print1(p, ", ")); ); } \\ Michel Marcus, Sep 25 2014

CROSSREFS

Cf. A001359, A038878.

Sequence in context: A260260 A067985 A118873 * A162834 A145980 A142622

Adjacent sequences:  A247871 A247872 A247873 * A247875 A247876 A247877

KEYWORD

nonn

AUTHOR

Zak Seidov, Sep 25 2014

STATUS

approved

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Last modified October 15 05:43 EDT 2019. Contains 328026 sequences. (Running on oeis4.)