4 problems

Let a coin system be a finite sequence of coin values, and say that it has pattern $(+++-\cdots -+)$ when its successive change-making behavior has this sign pattern. Let…

Finite obstruction conjecture. There is a finite list of tournaments that are minimally not dominance graphs of systems of coins.

Let a $+/-$-class be a class of orderly currencies determined by a specified $+/-$ pattern, and suppose that this class is non-empty. Representative-with-first-coin-two conjecture.…

Let $A=(1,a_1,\ldots,a_k)$ be an orderly currency, and let $P=\{0,1,2,l\}$ be a type-4 set with $4\leq l\leq k$. The sub-currency determined by $P$ is $(1,a_1,a_2,a_l)$. Type-4 sub…