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Search: id:A154689
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| A154689 |
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Numbers n such that sigma_0(n-sigma_0(n))= sigma_0(n) |
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+0
1
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| 5, 7, 10, 13, 14, 18, 19, 26, 31, 38, 39, 43, 50, 55, 61, 62, 69, 72, 73, 78, 84, 86, 91, 95, 96, 98, 103, 108, 109, 110, 115, 119, 122, 123, 129, 133, 136, 138, 139, 145, 146, 151, 153, 159, 181, 182, 187, 190, 193, 199, 205, 206, 209, 213, 217, 218, 219, 221, 229
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A000005(n-A00000(n)) = A000005(n). Primes in this sequence is A006512.
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REFERENCES
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Jean-Marie De Koninck and Florian Luca: Positive Integers n Such That sigma_0(phi(n)) = sigma_0(n), Journal of Integer Sequences, Vol. 11 (2008), Article 08.1.5.
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LINKS
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J.-M. de Koninck, F. Luca, Positive integers n such that sigma(phi(n))=sigma(n), J. Int. Seq. vol 11 (2008), #08.1.5. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 15 2009]
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MAPLE
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A000005 := proc(n) numtheory[tau](n) ; end: for n from 1 to 1000 do a05 := A000005(n) ; if A000005(n-a05) = a05 then printf("%d, ", n) ; fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 15 2009]
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CROSSREFS
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Cf. A000005,A006512
Sequence in context: A066513 A028810 A097700 this_sequence A024325 A060873 A112251
Adjacent sequences: A154686 A154687 A154688 this_sequence A154690 A154691 A154692
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KEYWORD
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easy,nonn
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AUTHOR
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Ctibor O. Zizka (c.zizka(AT)email.cz), Jan 14 2009
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EXTENSIONS
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Extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 15 2009
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