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A330366
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Prime numbers p_k such that p_k == 1 (mod 10) and p_(k+1) == 1 (mod 10).
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6
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181, 241, 421, 631, 691, 811, 1021, 1051, 1171, 1471, 1801, 2521, 2731, 3001, 3361, 3571, 4201, 4231, 4261, 4831, 4861, 5011, 5351, 5581, 5701, 5791, 6091, 6121, 6301, 6481, 6491, 6691, 6781, 7321, 8101, 8221, 8821, 8941, 9421, 9511, 9931, 10141, 10321, 10771, 11161, 11971
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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First @ Transpose @ Select[Partition[Select[Range[13500], PrimeQ], 2, 1], Mod[First[#], 10] == 1 && Mod[Last[#], 10] == 1 &] (* Amiram Eldar, Jan 20 2020 *)
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PROG
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(PARI) isok(p) = isprime(p) && ((p % 10)==1) && ((nextprime(p+1) % 10) == 1); \\ Michel Marcus, Jan 20 2020
(Magma) [p: p in PrimesUpTo(14000)| (p mod 10 eq 1) and (NextPrime(p) mod 10 eq 1)]; // Marius A. Burtea, Jan 20 2020
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CROSSREFS
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Cf. A030430 (1, any), this sequence (1, 1), A331555 (1, 3), A331324 (1, 7), A030431 (3, any), A030432 (7, any), A030433 (9, any) [where (a, b) means p_k == a (mod 10) and p_(k+1) == b (mod 10)].
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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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