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%I #5 Mar 30 2012 18:39:02
%S 0,1,2,2,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,6,6,6,6,6,6,6,8,9,
%T 10,10,10,13,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,
%U 16,16,16,16,16,16,16,16,16,16,16,20,20,22,22,22,22,23,23,23,23,23,23
%N Number of pairs (x,y) such that prime(x) + prime(y) = x*tau(x) + y*tau(y), 1<=x<=y<=n.
%o (PARI) for(n=1,130,print1(sum(i=1,n,sum(j=1,i,if(prime(i)+prime(j)-i*numdiv(i)-j*numdiv(j),0,1))),","))
%Y Cf. A000005.
%K nonn
%O 1,3
%A _Benoit Cloitre_, Jun 06 2002
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