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%I #29 Dec 15 2017 17:36:07
%S 1,3,5,7,9,11,15,21,315,1155,8925,32445,442365,815634435
%N Odd numbers whose abundance b satisfies -10 <= b <= 10, where the abundance of a number n is A(n) = sigma(n) - 2n.
%C Apart from {1, 3, 5, 7, 9, 11, 15, 21, 315}, subset of A088012. Probably finite. - _Charles R Greathouse IV_, Mar 28 2011
%C a(15) > 10^13. - _Giovanni Resta_, Mar 29 2013
%C The abundance of the given terms a(1..14) is: (-1, -2, -4, -6, -5, -10, -6, -10, -6, -6, 6, 6, 6, -6). See also A171929, A188263 and A188597 for numbers with abundancy sigma(n)/n close to 2. - _M. F. Hasler_, Feb 21 2017
%C a(15) > 10^22. - _Wenjie Fang_, Jul 13 2017
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Abundance.html">Abundance</a>
%e sigma(32445) = 64896 and 32445*2 = 64890, which makes the odd number 32445 six away from perfection: A(32445) = 6 and hence in this sequence.
%t Select[Range[1, 10^6, 2], -10 <= DivisorSigma[1, #] - 2 # <= 10 &] (* _Michael De Vlieger_, Feb 22 2017 *)
%o (PARI) forstep(n=1,442365,2,if(abs(sigma(n)-2*n)<=10,print1(n,",")))
%Y Cf. A033879, A033880, A000203, A088012.
%K nonn
%O 1,2
%A _Jason Earls_, Nov 30 2002
%E 815634435 from _Farideh Firoozbakht_, Jan 12 2004
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