Concepts2
βMathAdvanced
MΓΆbius Function and Inversion
The MΓΆbius function ΞΌ(n) is 0 if n has a squared prime factor, otherwise it is (-1)^k where k is the number of distinct prime factors.
#mobius function#mobius inversion#dirichlet convolution+12
βMathAdvanced
Divisor Function Sums
Summing the divisor function d(i) up to n equals counting lattice points under the hyperbola xy β€ n, which can be done in O(βn) using floor-division blocks.
#divisor function#euler totient#mobius function+11