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%I #14 Feb 06 2016 09:47:22
%S 42,51,123,141,204,371,497,708,923,992,1034,1343,1391,1484,1595,1691,
%T 1826,3266,3317,5015,5152,7367,8003,9132,9287,9494,11078,13223,15458,
%U 15833,17975,18752,19428,20120,20915,21251,21566,24119,24503,25787
%N Numbers m having the same sum of divisors as m+20 has.
%C A000203(a(n)) = A000203(a(n) + 20).
%D J.-M. De Koninck, Those Fascinating Numbers, Amer. Math. Soc., 2009, page 16.
%H Reinhard Zumkeller and Donovan Johnson, <a href="/A181647/b181647.txt">Table of n, a(n) for n = 1..1000</a> (first 100 terms from Reinhard Zumkeller)
%H A. Weingartner, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL14/Weingartner/wein3.html">On the Solutions of sigma(n) = sigma(n+k)</a>, Journal of Integer Sequences, Vol. 14 (2011), #11.5.5.
%e a(1)=42, divisors(42)={1,2,3,6,7,14,21,42}, divisors(42+20)={1,2,31,62}: 1+2+3+6+7+14+21+42=1+2+31+62.
%o (PARI) isok(n) = sigma(n) == sigma(n+20); \\ _Michel Marcus_, Feb 06 2016
%Y Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015876, A015877, A015880, A015881, A015882, A015883.
%K nonn
%O 1,1
%A _Reinhard Zumkeller_, Nov 03 2010
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