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A071805
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Number of pairs (x,y) such that prime(x) + prime(y) = x*tau(x) + y*tau(y), 1<=x<=y<=n.
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0
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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, 10, 10, 10, 13, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 20, 20, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23
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OFFSET
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1,3
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LINKS
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PROG
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(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))), ", "))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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