## The Star of David Rule

Sun, Yidong
##### Description
In this note, a new concept called {\em $SDR$-matrix} is proposed, which is an infinite lower triangular matrix obeying the generalized rule of David star. Some basic properties of $SDR$-matrices are discussed and two conjectures on $SDR$-matrices are presented, one of which states that if a matrix is a $SDR$-matrix, then so is its matrix inverse (if exists).
Comment: 7 pages, 1 figure
##### Keywords
Mathematics - Combinatorics, 05A10, 15A09