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- # Sum of the numbers of divisors of gcd(x,y) with x*y <= n
- # https://oeis.org/A268732
- # a(n) = Sum_{k=1..floor(sqrt(n))} (2*Sum_{j=1..floor(sqrt(n/k^2))} floor(n/(j*k^2)) - floor(sqrt(n/k^2))^2). - ~~~~
- (PARI) a(n) = sum(k=1, sqrtint(n), 2*sum(j=1, sqrtint(n\(k*k)), n\(j*k*k))-sqrtint(n\(k*k))^2); \\ ~~~~
- a(10^9) = 32467409097
- a(10^10) = 362549612240
- a(10^11) = 4004254692640
- a(10^12) = 43830142939380
- a(10^13) = 476177421208658
- a(10^14) = 5140534231877816
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