

A088833


Numbers n whose abundance is 8: sigma(n)  2n = 8.


18



56, 368, 836, 11096, 17816, 45356, 77744, 91388, 128768, 254012, 388076, 2087936, 2291936, 13174976, 29465852, 35021696, 45335936, 120888092, 260378492, 381236216, 775397948, 3381872252, 4856970752, 6800228816, 8589344768, 44257207676, 114141404156
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OFFSET

1,1


COMMENTS

A subset of A045770.
If p=2^m9 is prime (m is in the sequence A059610) then n=2^(m1)*p is in the sequence. See comment lines of the sequence A088831. 56, 368, 128768, 2087936 & 8589344768 are of the mentioned form.  Farideh Firoozbakht, Feb 15 2008
a(28) > 10^12.  Donovan Johnson, Dec 08 2011
a(31) > 10^13.  Giovanni Resta, Mar 29 2013
a(38) > 10^18.  Hiroaki Yamanouchi, Aug 23 2018
Any term x of this sequence can be combined with any term y of A125247 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

Giovanni Resta and Hiroaki Yamanouchi, Table of n, a(n) for n = 1..37 (terms a(1)a(30) from Giovanni Resta)


EXAMPLE

Except first 2 terms of A045770 (10 and 49) are here:abundances={2,41,8,8,8,8,8,8,8,8,8,8,8,8,8}.


MATHEMATICA

Do[If[DivisorSigma[1, n]==2n+8, Print[n]], {n, 100000000}] (* Farideh Firoozbakht, Feb 15 2008 *)


PROG

(PARI) is(n)=sigma(n)==2*n+8 \\ Charles R Greathouse IV, Feb 21 2017


CROSSREFS

Cf. A033880, A045668, A045669, A088831, A088832, A059610, A125247 (deficiency 8).
Sequence in context: A219718 A296823 A003783 * A181598 A181705 A219826
Adjacent sequences: A088830 A088831 A088832 * A088834 A088835 A088836


KEYWORD

nonn


AUTHOR

Labos Elemer, Oct 28 2003


EXTENSIONS

a(14)a(17) from Farideh Firoozbakht, Feb 15 2008
a(18)a(25) from Donovan Johnson, Dec 23 2008
a(26)a(27) from Donovan Johnson, Dec 08 2011


STATUS

approved



