# Pascal's approach.
G! ← ⍥(˜⊂^0⊸⊣)-1⧻⊸⊢
⍉G!(↘¯1⬚0⧈+)⬚0˜↯[1]⊂1 5
G!(↘¯1⬚0⧈+)⬚0˜↯[1]⊂1 5
G!(\+)˜↯1⊂1 5

# Combinatorial approach.
T ← ⧅>
˙⊞T⇡5
⍉˙⊞T⇡5
≡≡T⍉↯[⟜∘]⟜⇡ ⟜(˙⊞+⇡)5