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A108605
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Semiprimes with prime sum of factors.
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8
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6, 10, 22, 34, 58, 82, 118, 142, 202, 214, 274, 298, 358, 382, 394, 454, 478, 538, 562, 622, 694, 838, 862, 922, 1042, 1138, 1198, 1234, 1282, 1318, 1618, 1642, 1654, 1714, 1762, 2038, 2062, 2098, 2122, 2182, 2302, 2458, 2554, 2578, 2602, 2638, 2854, 2902
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| All terms are even.
The definition implies that the sum of factors is the sum over the prime factors with multiplicity, as in A001414. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 28 2008
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FORMULA
| a(n)=2*p, with p and 2+p twin primes; a(n)=2*A001359(n).
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EXAMPLE
| 58=2*29 and 2+29 is prime.
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MATHEMATICA
| Select[Range[2, 3000, 2], !IntegerQ[Sqrt[ # ]]&&Plus@@(Transpose[FactorInteger[ # ]])[[2]]==2&&PrimeQ[Plus@@(Transpose[FactorInteger[ # ]])[[1]]]&]
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CROSSREFS
| Cf. A001358 semiprimes, A001359 lesser of twin primes, A101605 3-almost primes, A108606 semiprimes with prime sum of digits, A108607 intersection of A108605 and A108606.
Sequence in context: A189992 A082917 A001172 * A063765 A085712 A179875
Adjacent sequences: A108602 A108603 A108604 * A108606 A108607 A108608
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KEYWORD
| easy,nonn
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Jun 12 2005
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EXTENSIONS
| Changed division by 2 to multiplication by 2 in formula related to A001359. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 28 2008
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