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A005114
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Untouchable numbers: impossible values for sum of aliquot parts of n.
(Formerly M1552)
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25
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2, 5, 52, 88, 96, 120, 124, 146, 162, 188, 206, 210, 216, 238, 246, 248, 262, 268, 276, 288, 290, 292, 304, 306, 322, 324, 326, 336, 342, 372, 406, 408, 426, 430, 448, 472, 474, 498, 516, 518, 520, 530, 540, 552, 556, 562, 576, 584, 612, 624, 626, 628, 658
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 840.
P. Erdos, Ueber die Zahlen der Form sigma(n)-n und n-phi(n). Elemente der Math. 28 (1973), 83-86.
R. K. Guy, Unsolved Problems in Number Theory, B10.
Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 65.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Klaus Brockhaus, Table of n, a(n) for n = 1,...,8153
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
Wikipedia, Untouchable number
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FORMULA
| Complement of A078923. - Lekraj Beedassy (blekraj(AT)yahoo.com), Jul 19 2005
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PROG
| (PARI) isA078923(n)= { if(n==0 || n==1, return(1) ; ) ; for(m=1, (n-1)^2, if( sigma(m)-m == n, return(1) ; ) ; ) ; return(0) ; } isA005114(n)= { return(!isA078923(n)) ; } { for(n=1, 700, if (isA005114(n), print(n) ; ) ; ) ; } - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 10 2006
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CROSSREFS
| Sequence in context: A099658 A102011 A004098 * A081090 A071880 A071882
Adjacent sequences: A005111 A005112 A005113 * A005115 A005116 A005117
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KEYWORD
| nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from David W. Wilson (davidwwilson(AT)comcast.net)
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