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A141645 Numbers n such that sigma(n)/n = 9/2.

%I A141645 #13 Apr 19 2016 01:07:36
%S A141645 8910720,17428320,8583644160,57629644800,206166804480,
%T A141645 1416963251404800,15338300494970880,6275163455171297280,
%U A141645 200286975596707184640,215594611071909888000,5997579964837140234240,39887491844324122951680
%N A141645 Numbers n such that sigma(n)/n = 9/2.
%C A141645 200286975596707184640 belongs to this sequence. - _Gerard P. Michon_, May 10 2009
%C A141645 81703797123392614369698250752 is in this sequence. - _Gerard P. Michon_, May 11 2009
%H A141645 G. P. Michon, <a href="/A141645/b141645.txt">Table of n, a(n) for n = 1..27</a>
%H A141645 G. P. Michon, <a href="http://www.numericana.com/answer/numbers.htm#multiperfect">Multiperfect and hemiperfect integers</a> [From _Gerard P. Michon_, Jun 04 2009]
%H A141645 Walter Nissen, <a href="http://upforthecount.com/math/abundance.html">Abundancy : Some Resources </a>
%o A141645 (PARI) is(n)=sigma(n,-1)==9/2 \\ _Charles R Greathouse IV_, Mar 09 2014
%Y A141645 Cf. A055153, A141643, A159271, A160678.
%Y A141645 Cf. A159907 = (half-integer abundancy). - _Gerard P. Michon_, May 10 2009
%K A141645 nonn
%O A141645 1,1
%A A141645 _Yasutoshi Kohmoto_, May 10 2008
%E A141645 Definition rewritten by _M. F. Hasler_, May 10 2008
%E A141645 Is it certain that there are no other terms below the highest value shown? - _N. J. A. Sloane_, Sep 07 2008
%E A141645 a(1) corrected and a(3) confirmed by _Ray Chandler_, Sep 18 2008
%E A141645 Missing term a(2)=17428320 communicated by _Walter Nissen_, Apr 17 2009. There are no further terms through 2^34.
%E A141645 Missing term a(4) inserted and a(6) and a(8) added by Grzegorz Lach (137.036(AT)gmail.com), Apr 18 2009. a(4) was also sent by Avinoam Kalma (a.kalma(AT)gmail.com), Apr 20 2009.
%E A141645 a(7) = 15338300494970880 added by _Gerard P. Michon_, May 10 2009.
%E A141645 a(10)=215594611071909888000 [and above] from _Michel Marcus_, added by _Gerard P. Michon_, Jun 04 2009