For an integer x let tx denote the triangular number x(x+1)/2.
Following a recent work of Z. W. Sun, we show that every natural number can be
written in any of the following forms with x,y,z∈Z: x2+3y2+tz,x2+3ty+tz,x2+6ty+tz,3x2+2ty+tz,4x2+2ty+tz. This confirms a
conjecture of Sun.