{3，4^＊}-PBD的存在性

Existence of { 3,4^＊ } - PBD

主要解决{3,4*}-PBD的存在性问题。当且仅当:(1)v≥4;(2)v≡0,1(mod3)且v≠6,7,9时,即{3,4*}-PBD存在。

Combinatorial design theory is an important branch of modem combinatorial theory. The research of design refers to a very important and .central problem of combinatorial theory. That is to say we must arrange some things by certain rule. The existence problem of {3,4^＊}-PBD is solved：{ 3,4^＊}-PBD exist if and only if （1）v≥4; （2） v = 0,1（rood 3） and v≠ 6,7,9.