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A075705
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Safe primes (A005385) (p and (p-1)/2 are primes) such that 6*p+1 is also prime.
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1
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5, 7, 11, 23, 47, 83, 107, 263, 347, 467, 503, 863, 887, 1283, 1487, 1823, 1907, 2027, 2063, 2447, 2903, 3203, 3623, 4007, 4127, 4547, 4703, 4787, 5387, 5807, 7523, 7703, 8147, 8423, 11423, 11483, 11807, 12107, 12227, 12647, 12983, 13043, 13163, 14087, 14207
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| David Consiglio, Jr. and T. D. Noe, Table of n, a(n) for n = 1..1000
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EXAMPLE
| 47 is prime, so is (47-1)/2=23 and also 6*47+1=283; 83 is a prime, (83-1)/2=41 and 6*83+1=499, ...
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MAPLE
| ts_sg_var_pras := proc(nmax) local i, tren, atek; tren := 0: for i from 1 to nmax do atek := numtheory[safeprime](i): if (atek > tren) then if (isprime(atek)='true' and isprime(6*atek+1)='true') then tren := atek: fi; fi; od; end: seq(ts_sg_var_pras(i), i=1..3000);
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MATHEMATICA
| Select[Range[20000], PrimeQ[#] && PrimeQ[(#-1)/2] && PrimeQ[6#+1] &] (* T. D. Noe, Nov 07 2011 *)
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CROSSREFS
| Cf. A005384, A005385, A059455, A007693.
Sequence in context: A092307 A005385 A181602 * A141305 A067289 A036491
Adjacent sequences: A075702 A075703 A075704 * A075706 A075707 A075708
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KEYWORD
| nonn
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AUTHOR
| Jani Melik (jani_melik(AT)hotmail.com), Oct 02 2002
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