n·C_(2P)的优美性

n·are Graceful

是一个有向ｍ回路，ｎ个恰有一个公共点组成的图，记作ｎ·证明了ｎ·是优美图，给出了ｎ· 是优美图的必要条件，并猜想：当ｎ≡０（ｍｏｄ２）时，ｎ·是优美图。

is a directed circuit.The graph composed of n· with one same vertex is de-noted by n· . This paper shows that n· (p∈N,p≥2)is gracelul,and gets the necessarycondition for n·(m,n∈N)to be graceful.If n≡0(mod 2),we conjecture that n· isgraceful.