

A223609


Numbers n whose abundance is 10. Sigma(n)2*n = 10.


5




OFFSET

1,1


COMMENTS

Suggested by N. J. A. Sloane and Robert G. Wilson v.
a(5) > 10^12.
a(5) > 10^13.  Giovanni Resta, Mar 29 2013
a(5) > 10^18.  Hiroaki Yamanouchi, Aug 23 2018
Any term x of this sequence can be combined with any term y of A101223 to satisfy the property (sigma(x)+sigma(y))/(x+y) = 2, which is a necessary (but not sufficient) condition for two numbers to be amicable.  Timothy L. Tiffin, Sep 13 2016


LINKS

Table of n, a(n) for n=1..4.


EXAMPLE

n = 34358296576. sigma(n)2*n = 10.


MATHEMATICA

Select[Range[1, 10^8], DivisorSigma[1, #]  2 # == 10 &] (* Vincenzo Librandi, Sep 15 2016 *)


PROG

(PARI) for(n=1, 10^8, if(sigma(n)2*n==10, print1(n ", ")))
(MAGMA) [n: n in [1..9*10^6]  (SumOfDivisors(n)2*n) eq 10]; // Vincenzo Librandi, Sep 15 2016


CROSSREFS

Cf. A000203, A033880, A101223 (deficiency 10).
Sequence in context: A278431 A229584 A140702 * A145294 A147520 A190926
Adjacent sequences: A223606 A223607 A223608 * A223610 A223611 A223612


KEYWORD

nonn,more


AUTHOR

Donovan Johnson, Mar 23 2013


STATUS

approved



