%I #13 Apr 19 2016 01:07:36

%S 8910720,17428320,8583644160,57629644800,206166804480,

%T 1416963251404800,15338300494970880,6275163455171297280,

%U 200286975596707184640,215594611071909888000,5997579964837140234240,39887491844324122951680

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

%C 200286975596707184640 belongs to this sequence. - _Gerard P. Michon_, May 10 2009

%C 81703797123392614369698250752 is in this sequence. - _Gerard P. Michon_, May 11 2009

%H G. P. Michon, <a href="/A141645/b141645.txt">Table of n, a(n) for n = 1..27</a>

%H 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 Walter Nissen, <a href="http://upforthecount.com/math/abundance.html">Abundancy : Some Resources </a>

%o (PARI) is(n)=sigma(n,-1)==9/2 \\ _Charles R Greathouse IV_, Mar 09 2014

%Y Cf. A055153, A141643, A159271, A160678.

%Y Cf. A159907 = (half-integer abundancy). - _Gerard P. Michon_, May 10 2009

%K nonn

%O 1,1

%A _Yasutoshi Kohmoto_, May 10 2008

%E Definition rewritten by _M. F. Hasler_, May 10 2008

%E Is it certain that there are no other terms below the highest value shown? - _N. J. A. Sloane_, Sep 07 2008

%E a(1) corrected and a(3) confirmed by _Ray Chandler_, Sep 18 2008

%E Missing term a(2)=17428320 communicated by _Walter Nissen_, Apr 17 2009. There are no further terms through 2^34.

%E 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 a(7) = 15338300494970880 added by _Gerard P. Michon_, May 10 2009.

%E a(10)=215594611071909888000 [and above] from _Michel Marcus_, added by _Gerard P. Michon_, Jun 04 2009