S ← |3 memo⍣(
  ⋅+ ⟜°0
| ⋅⊙◌ ◡⋅⋅°0
| S⊃(-1|S⊙⊙-₁|+S⊸(⊙⊙-₁)))
≡(&p$"_ _"⟜(S°⊟₃)) [0_0_0 1_1_1 2_1_1 3_1_1 2_2_1]