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A156658
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Primes p such that also 2*p+1 or (p-1)/2 is prime.
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3
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2, 3, 5, 7, 11, 23, 29, 41, 47, 53, 59, 83, 89, 107, 113, 131, 167, 173, 179, 191, 227, 233, 239, 251, 263, 281, 293, 347, 359, 383, 419, 431, 443, 467, 479, 491, 503, 509, 563, 587, 593, 641, 653, 659, 683, 719, 743, 761, 809, 839, 863, 887, 911, 953, 983, 1013
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OFFSET
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1,1
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COMMENTS
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primes occurring in Cunningham chains of the first kind.
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LINKS
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MAPLE
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select(t -> isprime(t) and (isprime(2*t+1) or isprime((t-1)/2)), [2, seq(p, p=3..10000, 2)]); # Robert Israel, May 03 2016
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MATHEMATICA
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Select[Prime@ Range@ 180, PrimeQ[2 # + 1] || PrimeQ[(# - 1)/2] &] (* Michael De Vlieger, Apr 06 2016 *)
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PROG
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(PARI) lista(nn) = {forprime(p=2, nn, if (isprime(2*p+1) || isprime((p-1)/2), print1(p, ", ")); ); } \\ Michel Marcus, Apr 06 2016
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CROSSREFS
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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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