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A223609 Numbers n whose abundance is 10. Sigma(n)-2*n = 10. 5
40, 1696, 518656, 34358296576 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
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
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
KEYWORD
nonn,more
AUTHOR
Donovan Johnson, Mar 23 2013
STATUS
approved

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Last modified December 7 18:28 EST 2023. Contains 367660 sequences. (Running on oeis4.)