English

The parametric Frobenius problem and parametric exclusion

Combinatorics 2016-11-08 v3

Abstract

The Frobenius number of relatively prime positive integers a1,,ana_1, \ldots, a_n is the largest integer that is not a nononegative integer combination of the ai.a_i. Given positive integers a1,,ana_1, \ldots, a_n with n2,n \ge 2, the set of multiples of gcd(a1,,an)\gcd(a_1, \ldots, a_n) which have less than mm distinct representations as a nonnegative integer combination of the aia_i is bounded above, so we define fm,(a1,,an)f_{m, \ell}(a_1, \ldots, a_n) to be the th\ell^{\text{th}} largest multiple of gcd(a1,,an)\gcd(a_1, \ldots, a_n) with less than mm distinct representations (which generalizes the Frobenius number) and gm(a1,,an)g_m(a_1, \ldots, a_n) to be the number of positive multiples of gcd(a1,,an)\gcd(a_1, \ldots, a_n) with less than mm distinct representations. In the parametric Frobenius problem, the arguments are polynomials. Let P1,,PnP_1, \ldots, P_n be integer valued polynomials of one variable which are eventually positive. We prove that fm,(P1(t),,Pn(t))f_{m, \ell}(P_1(t), \ldots, P_n(t)) and gm(P1(t),,Pn(t)),g_m(P_1(t), \ldots, P_n(t)), as functions of t,t, are eventually quasi-polynomial. A function hh is eventually quasi-polynomial if there exist dd and polynomials R0,,Rd1R_0, \ldots, R_{d-1} such that for such that for sufficiently large integers t,t, h(t)=Rt(modd)(t).h(t)=R_{t \pmod{d}}(t). We do so by formulating a type of parametric problem that generalizes the parametric Frobenius Problem, which we call a parametric exclusion problem. We prove that the th\ell^{\text{th}} largest value of some polynomial objective function, with multiplicity, for a parametric exclusion problem and the size of its feasible set are eventually quasi-polynomial functions of t.t.

Keywords

Cite

@article{arxiv.1510.01349,
  title  = {The parametric Frobenius problem and parametric exclusion},
  author = {Bobby Shen},
  journal= {arXiv preprint arXiv:1510.01349},
  year   = {2016}
}

Comments

27 pages, second version

R2 v1 2026-06-22T11:13:19.521Z