|
%I #20 Apr 04 2019 03:01:42
%S 24,91963648,10200236032
%N Numbers n such that sigma(n)/n = 5/2.
%C There are no other terms through 2^34. - _Walter Nissen_, Apr 17 2009
%C No more terms below 10^12. - _Jud McCranie_, Aug 30 2013
%H G. P. Michon, <a href="http://www.numericana.com/answer/numbers.htm#multiperfect">Multiperfect and hemiperfect numbers</a>
%H Walter Nissen, <a href="http://upforthecount.com/math/abundance.html">Abundancy : Some Resources </a>
%H Walter Nissen, <a href="http://upforthecount.com/math/abundance.html">Abundancy : Some Resources </a>
%H Walter Nissen, <a href="http://upforthecount.com/math/ffp8.html">Primitive Friendly Pairs with friends < 2^34 with denom < 20000</a>
%t Select[Range[100000], DivisorSigma[1, #]/# == 5/2 &] (* _Robert Price_, Apr 03 2019 *)
%o (PARI) isok(n) = sigma(n, -1) == 5/2; \\ _Michel Marcus_, Apr 04 2019
%Y Cf. A055153, A141645, A159271, A160678.
%K nonn,more,bref
%O 1,1
%A _Yasutoshi Kohmoto_, May 10 2008
%E Definition rewritten by _M. F. Hasler_, May 10 2008
%E First three terms confirmed by _Ray Chandler_, Sep 18 2008
| 