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%I #25 Dec 13 2020 05:14:53
%S 0,0,0,0,0,0,0,1,1,1,2,3,5,7,8,9,16,22,30,42,57,68,95,133,167,205,257,
%T 342,460,605,786,1043,1356,1749,2294,2905,3757,4811,6181,7893,10146,
%U 13051,16762,21396,27380,34939,44449,56481,71453,90783,115200,145702,184045,232899,294326,372216
%N Number of amicable pairs with lesser member at most 2^n.
%C Sergei Chernykh led a BOINC project to find a(64) = 2390655. The project took 7 months and used several hundred CPU-years of computation time.
%H Amiram Eldar, <a href="/A290985/b290985.txt">Table of n, a(n) for n = 1..66</a> (calculated from Chernykh's database)
%H Sergei Chernykh, <a href="https://sech.me/boinc/Amicable/">Amicable Numbers</a>.
%o (PARI) has(n,f=factor(n))=my(t=sigma(f)-n); t>n && sigma(t)==n+t
%o a(n)=my(s); forfactored(k=1,2^n, if(has(k[1],k[2]), s++)); s
%Y Cf. A002025, A066873, A259180.
%K nonn,hard
%O 1,11
%A _Charles R Greathouse IV_, Aug 16 2017
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