English

The Frobenius Formula for $A=(a,ha+d,ha+b_2d,...,ha+b_kd)$

Combinatorics 2026-04-13 v2 Number Theory

Abstract

Given relative prime positive integers A=(a1,a2,...,an)A=(a_1, a_2, ..., a_n), the Frobenius number g(A)g(A) is the largest integer not representable as a linear combination of the aia_i's with nonnegative integer coefficients. We find the ``Stable" property introduced for the square sequence A=(a,a+1,a+22,,a+k2)A=(a,a+1,a+2^2,\dots, a+k^2) naturally extends for A(a)=(a,ha+dB)=(a,ha+d,ha+b2d,...,ha+bkd)A(a)=(a,ha+dB)=(a,ha+d,ha+b_2d,...,ha+b_kd). This gives a parallel characterization of g(A(a))g(A(a)) as a ``congruence class function" modulo bkb_k when aa is large enough. For orderly sequence B=(1,b2,,bk)B=(1,b_2,\dots,b_k), we find good bound for aa. In particular we calculate g(a,ha+dB)g(a,ha+dB) for B=(1,2,b,b+1)B=(1,2,b,b+1), B=(1,2,b,b+1,2b)B=(1,2,b,b+1,2b), B=(1,b,2b1)B=(1,b,2b-1) and B=(1,2,...,k,K)B=(1,2,...,k,K). Our idea also applies to the case B=(b1,b2,...,bk)B=(b_1,b_2,...,b_k), b1>1b_1> 1.

Keywords

Cite

@article{arxiv.2304.09039,
  title  = {The Frobenius Formula for $A=(a,ha+d,ha+b_2d,...,ha+b_kd)$},
  author = {Feihu Liu and Guoce Xin and Suting Ye and Jingjing Yin},
  journal= {arXiv preprint arXiv:2304.09039},
  year   = {2026}
}