An equilateral triangle’s side length is uniquely determined by the number of equilateral triangles collinear going down in the middle of that arbitrary triangle. For example, a 2x2 side length triangle has two triangles or a rhombus in a straight line. For example, in a 4x4 needing 2x2 triangles, we have floor[1/2]+2/2+floor[3/2]+4/2+floor[3/2]+2/2+floor[1/2]=6. So generally, we have 1/1+2/1+…+9/1+10/1+9/1+…+1/1=100 of side length 1, similarly 45 of side length 2, +27 length 3, +18, +12, +9, +7, +5, +3, +1 =$\boxed{227}$ equilateral triangles.