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- #!/usr/bin/ruby
- # PARI/GP programs
- # a(n) = n - sum(k=1, sqrtint(n), moebius(k) * (n\k^2));
- # a(n) = my(s=0); forsquarefree(k=1, sqrtint(n), s += (-1)^(#k[2]~) * (n\k[1]^2)); n - s;
- func a(n) {
- n.nonsquarefree_count
- }
- func b(n) {
- n - sum(1..n.isqrt, {|k|
- moebius(k) * floor(n / k**2)
- })
- }
- func f(n) { # incorrect formula
- var s = 0
- each_prime(1..n.isqrt, {|p|
- s += idiv(n, p**2)
- })
- s
- }
- say 40.of(a)
- say 40.of(b)
- say 40.of(f)
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