Let B3(n) denote the number of partition triples of n where each partition is 3-core. With the help of generating function manipulations, we find several infinite families of arithmetic identities and congruences for B3(n). Moreover, let ω(n) denote the number of representations of a non-negative integer n in the form x21+x22+x23+3y21+3y22+3y23 with x1,x2,x3,y1,y2,y3∈ℤ. We find three arithmetic relations between B3(n) and ω(n), such as ω(6n+5)=4B3(6n+4).