Search: id:A005114
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%I A005114 M1552
%S A005114 2,5,52,88,96,120,124,146,162,188,206,210,216,238,246,248,262,268,276,
%T A005114 288,290,292,304,306,322,324,326,336,342,372,406,408,426,430,448,472,
%U A005114 474,498,516,518,520,530,540,552,556,562,576,584,612,624,626,628,658
%N A005114 Untouchable numbers: impossible values for sum of aliquot parts of n.
%D A005114 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005114 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.
%D A005114 P. Erdos, Ueber die Zahlen der Form sigma(n)-n und n-phi(n). Elemente 
               der Math. 28 (1973), 83-86.
%D A005114 R. K. Guy, Unsolved Problems in Number Theory, B10.
%D A005114 Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 
               65.
%H A005114 Klaus Brockhaus, <a href="b005114.txt">Table of n, a(n) for n = 1,...,
               8153</a>
%H A005114 M. Abramowitz and I. A. Stegun, eds., <a href="http://www.nrbook.com/
               abramowitz_and_stegun/">Handbook of Mathematical Functions</a>, National 
               Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 
               [alternative scanned copy].
%H A005114 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               UntouchableNumber.html">Link to a section of The World of Mathematics.</
               a>
%H A005114 Wikipedia, <a href="http://en.wikipedia.org/wiki/Untouchable_number">
               Untouchable number</a>
%F A005114 Complement of A078923. - Lekraj Beedassy (blekraj(AT)yahoo.com), Jul 
               19 2005
%o A005114 (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
%Y A005114 Sequence in context: A099658 A102011 A004098 this_sequence A081090 A071880 
               A071882
%Y A005114 Adjacent sequences: A005111 A005112 A005113 this_sequence A005115 A005116 
               A005117
%K A005114 nonn,nice
%O A005114 1,1
%A A005114 N. J. A. Sloane (njas(AT)research.att.com).
%E A005114 More terms from David W. Wilson (davidwwilson(AT)comcast.net)

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