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 A141547 Numbers n whose abundance is 16. 7
 550, 748, 1504, 7192, 7912, 10792, 17272, 30592, 1713592, 4526272, 8353792, 9928792, 11547352, 17999992, 89283592, 173482552, 361702144, 1081850752, 1845991216, 2146926592, 11097907192, 12985220152, 21818579968, 34357510144, 109170719992, 228354264064, 279632332792, 549746900992 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Any term x of this sequence can be combined with any term y of A125248 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 a(41) > 10^18 - Hiroaki Yamanouchi, Aug 23 2018 LINKS Giovanni Resta and Hiroaki Yamanouchi, Table of n, a(n) for n = 1..40 (terms a(1)-a(32) from Giovanni Resta) EXAMPLE a(1) = 550, since sigma(550) - 2*550 = 1116 - 1100 = 16. - Timothy L. Tiffin, Sep 13 2016 MATHEMATICA lst={}; Do[If[n==Plus@@Divisors[n]-n-16, AppendTo[lst, n]], {n, 10^4}]; Print[lst]; lst = {}; Do[ If[2 n + 16 == DivisorSigma[1, n], AppendTo[lst, n]], {n, 10^8}]; lst (* Robert G. Wilson v, Aug 17 2008 *) Select[Range[1, 10^8], DivisorSigma[1, #] - 2 # == 16 &] (* Vincenzo Librandi, Sep 14 2016 *) PROG (Magma) [n: n in [1..9*10^6] | (SumOfDivisors(n)-2*n) eq 16]; // Vincenzo Librandi, Sep 14 2016 (PARI) is(n)=sigma(n)==2*n+16 \\ Charles R Greathouse IV, Feb 21 2017 CROSSREFS Cf. A125248 (deficiency 16). Sequence in context: A235585 A210399 A232314 * A236723 A189502 A190075 Adjacent sequences: A141544 A141545 A141546 * A141548 A141549 A141550 KEYWORD nonn AUTHOR Vladimir Joseph Stephan Orlovsky, Aug 16 2008 EXTENSIONS a(9)-a(14) from Robert G. Wilson v, Aug 17 2008 a(15)-a(24) from Donovan Johnson, Dec 21 2008 a(25)-a(28) from Donovan Johnson, Dec 08 2011 STATUS approved

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Last modified May 29 21:17 EDT 2023. Contains 363042 sequences. (Running on oeis4.)