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%I #12 Sep 28 2015 03:31:54
%S 10,14,32,58,154,182,382,758,3830,5962,67815454,94941602,7172169026,
%T 8196764584,18624907238,34790550682,30033199624,31387575416,
%U 38857270202,48571587730
%N Couple of numbers a, b for which sigma*(a)=b and sigma(b)-b=a, where sigma*(n) is the sum of the anti-divisors of n.
%C a(21) > 10^11. - _Hiroaki Yamanouchi_, Sep 28 2015
%e sigma*(10) = 3+4+7 = 14.
%e sigma(14)-14 = 1+2+7 = 10.
%e sigma*(32)= 3+5+7+9+13+21 = 58.
%e sigma(58)-58 = 1+2+29 = 32.
%p with(numtheory);
%p P:= proc(n)
%p local a,b,c,i,ks;
%p for i from 3 to n do
%p a:={};
%p for k from 2 to i-1 do
%p if abs((i mod k)- k/2) < 1 then
%p a:=a union {k};
%p fi;
%p od;
%p b:=nops(a); c:=op(a); s:=0;
%p for k from 1 to b do
%p s:=s+c[k];
%p od;
%p if sigma(s)-s=i then
%p print(i,s);
%p fi;
%p od;
%p end:
%p P(10000);
%Y Cf. A063990, A066272, A192290, A192292, A192293.
%K nonn,more
%O 1,1
%A _Paolo P. Lava_, Jun 29 2011
%E a(11)-a(20) from _Hiroaki Yamanouchi_, Sep 28 2015
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