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Search: id:A068016
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| A068016 |
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Lonely non-twin primes - non-twins sandwiched between two pairs of twins. |
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+0
1
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| 23, 37, 67, 233, 277, 631, 1039, 1283, 1297, 1307, 1613, 1693, 1709, 2099, 2137, 2333, 2719, 2797, 3271, 3533, 3547, 3571, 3923, 4027, 4253, 4523, 4643, 4793, 5483, 5507, 5647, 6563, 7321, 8831, 8849, 9007, 9029, 10061, 10079, 10289, 10513, 12049, 13687
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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37 is in the sequence because it is adjacent to two pairs of twins (29,31 and 41,43). 47 is not because the primes adjacent to it are 43 and 53 and although 43 is a twin, 53 is not.
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MATHEMATICA
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PrimeNext[n_]:=Module[{k}, k=n+1; While[ !PrimeQ[k], k++ ]; k]; PrimePrev[n_]:=Module[{k}, k=n-1; While[ !PrimeQ[k], k-- ]; k]; lst={}; Do[p=Prime[n]; If[ !PrimeQ[p-2]&&PrimeQ[PrimePrev[p]-2]&&!PrimeQ[p+2]&&PrimeQ[PrimeNext[p]+2], AppendTo[lst, p]], {n, 7!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Jul 22 2009]
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CROSSREFS
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Cf. A001097, A069453.
Sequence in context: A141521 A080906 A089685 this_sequence A140442 A078731 A133957
Adjacent sequences: A068013 A068014 A068015 this_sequence A068017 A068018 A068019
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KEYWORD
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nonn,new
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AUTHOR
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N. Fernandez (primeness(AT)borve.org), Mar 22 2002
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EXTENSIONS
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More terms from Vladimir Orlovsky (4vladimir(AT)gmail.com), Dec 04 2009
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