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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 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

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