# Additive divisor problem

The problem of finding asymptotic values for sums of the form:

$$ \tag{1} \left . { {\sum _ {m \leq n} \tau _{ {k _ 1}} ( m ) \tau _{ {k _ 2}} ( m + a ) ,} \atop {\sum _ {m < n}\tau _{ {k _ 1}} ( m ) \tau _{ {k _ 2}} ( n - m ) ,}} \right \} $$

where $ \tau _{k} (m) $ is the number of different factorizations of an integer $ m $ in $ k $ factors, counted according to multiplicity. Here $ k _{1} $ and $ k _{2} $ are integers $ \geq 2 $, $ a $ is a fixed integer different from zero and $ n $ is a sufficiently large number. In particular $ \tau _{2} (m) = \tau (m) $ is the number of divisors of the number $ m $. Sums of the form (1) express the number of solutions of the equations

$$ \tag{2} x _{1} \dots x _{ {k _ 2}} \ - \ y _{1} \dots y _{ {k _ 1}} \ = \ a , $$

$$ \tag{3} x _{1} \dots x _{ {k _ 1}} \ + \ y _{1} \dots y _{ {k _ 2}} \ = \ n , $$

respectively. Particular cases of the additive divisor problem ( $ k _{1} = k _{2} =2 $, $ k _{1} = 2 $ and $ k _{2} = 3 $) are considered in [1]–[3]. The additive divisor problem with $ k _{1} = 2 $ and an arbitrary positive integer $ k _{2} $ was solved using the dispersion method of Yu.V. Linnik [4].

#### Comments

The function $\tau_{2} (m) = \tau (m)$ is also denoted by $d (m)$ or $\sigma_{0} (m)$, cf. [a1], Sect. 16.7.

#### References

[1] | A.E. Ingham, "Some asymptotic formulae in the theory of numbers" J. London Math. Soc. (1) , 2 (1927) pp. 202–208 |

[2] | T. Esterman, "On the representations of a number as the sum of two products" Proc. London Math. Soc. (2) , 31 (1930) pp. 123–133 |

[3] | C. Hooly, "An asymptotic formula in the theory of numbers" Proc. London Math. Soc. (3) , 7 (1957) pp. 396–413 |

[4] | Yu.V. Linnik, "The dispersion method in binary additive problems" , Amer. Math. Soc. (1963) (Translated from Russian) |

[a1] | G.H. Hardy, E.M. Wright, "An introduction to the theory of numbers" , Clarendon Press (1979) |

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Additive divisor problem.

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