Concepts6

Groups

Möbius Function and Inversion

The Möbius function μ(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

∑MathAdvanced

Divisor Function Sums

Summing the divisor function d(i) up to n equals counting lattice points under the hyperbola xy ≤ n, which can be done in O(√n) using floor-division blocks.

#divisor function

Concepts6

Möbius Function and Inversion

Divisor Function Sums

Multiplicative Functions

Euler's Totient Function

Linear Sieve

Sieve of Eratosthenes