Search: id:A027687
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%I A027687
%S A027687 30240,32760,2178540,23569920,45532800,142990848,1379454720,43861478400,
               66433720320
%N A027687 Quadruply-perfect numbers: sum of divisors of n is 4n.
%D A027687 R. K. Guy, Unsolved Problems in Number Theory, B2.
%H A027687 T. D. Noe, <a href="b027687.txt">Table of n, a(n) for n=1..36</a> (complete 
               sequence)
%H A027687 Walter Nissen, <a href="http://upforthecount.com/math/abundance.html">
               Abundancy : Some Resources </a>
%H A027687 Achim Flammenkamp, <a href="http://www.uni-bielefeld.de/~achim/mpn.html">
               The Multiply Perfect Numbers Page</a>
%H A027687 Fred Helenius, <a href="http://pw1.netcom.com/~fredh/index.html">Link 
               to Glossary and Lists</a>
%H A027687 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               MultiperfectNumber.html">Link to a section of The World of Mathematics.</
               a>
%H A027687 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               Sous-Triple.html">Link to a section of The World of Mathematics.</
               a>
%t A027687 AbundantQ[n_]:=DivisorSigma[1, n]==4*n;a={};Do[If[AbundantQ[n], AppendTo[a, 
               n]], {n, 10^6}];a [From Vladimir Orlovsky (4vladimir(AT)gmail.com), 
               Aug 16 2008]
%Y A027687 Cf. A007539, A000396, A005820, A046060, A046061.
%Y A027687 Sequence in context: A104877 A027665 A113286 this_sequence A109485 A156429 
               A134118
%Y A027687 Adjacent sequences: A027684 A027685 A027686 this_sequence A027688 A027689 
               A027690
%K A027687 nonn,fini
%O A027687 1,1
%A A027687 Jean-Yves Perrier (nperrj(AT)ascom.ch)
%E A027687 4 more terms from Labos E. (labos(AT)ana.sote.hu)

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