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A070552
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Numbers n such that n and n+1 are semiprimes.
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24
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9, 14, 21, 25, 33, 34, 38, 57, 85, 86, 93, 94, 118, 121, 122, 133, 141, 142, 145, 158, 177, 201, 202, 205, 213, 214, 217, 218, 253, 298, 301, 302, 326, 334, 361, 381, 393, 394, 445, 446, 453, 481, 501, 514, 526, 537, 542, 553, 565, 622, 633, 634, 694, 697
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| A064911(a(n))*A064911(a(n)+1) = 1. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Dec 03 2009]
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LINKS
| D. W. Wilson, Table of n, a(n) for n = 1..10000
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MATHEMATICA
| f[n_]:=Last/@FactorInteger[n]=={1, 1}||Last/@FactorInteger[n]=={2}; lst={}; Do[If[f[n]&&f[n+1], AppendTo[lst, n]], {n, 7!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Feb 25 2010]
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PROG
| (PARI) forprime(p=3, 1e3, if(bigomega(2*p-1)==2, print1(2*p-1", ")); if(bigomega(2*p+1)==2, print1(2*p", "))) \\ Charles R Greathouse IV, Nov 09 2011
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CROSSREFS
| Cf. A001358, A007674, A039832.
Sequence in context: A006624 A184218 A186778 * A001198 A151915 A100263
Adjacent sequences: A070549 A070550 A070551 * A070553 A070554 A070555
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KEYWORD
| nonn
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AUTHOR
| Sharon Sela (sharonsela(AT)hotmail.com), May 03 2002
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), May 03 2002
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