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Search: id:A122483
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| A122483 |
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Numbers such that (-1)Sigma(m)*Sigma(m)= k*UnitaryPhi(m)*m for some integer k. |
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+0
2
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| 6, 140, 312, 1560, 14384, 18018, 40992, 2337400, 7012200, 11027016, 231402600
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If both 2^n-3 and 2^n-1 are prime them numbers of the form 2^(n-1)*(M_n-2)*M_n appear on the sequence, where M_n means Mersenne prime.
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EXAMPLE
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2^8*7*19*37*73*509, 2^8*5*7*19*37*509, 2^8*5^2*7*19*29*31*37*509, 2^9*3*11*31*1021, 2^9*3*7*11^2*19*31*131*1021, 2^11*3^6*5*7*13*23*137*467*1093*4093, 2^13*3*11*43*127*16381, 2^13*3*7*11^2*19*43*127*131*16381 But between 3*10^7 and them, many terms may lack.
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CROSSREFS
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Cf. A123124.
Sequence in context: A053467 A090944 A007340 this_sequence A123729 A123728 A012785
Adjacent sequences: A122480 A122481 A122482 this_sequence A122484 A122485 A122486
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KEYWORD
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nonn,more
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AUTHOR
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Yasutoshi Kohmoto zbi74583(AT)boat.zero.ad.jp, Sep 30 2006
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 01 2006
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