]runtime -c "{{⍵/⍨500≤{×/1+⊢⌿2 pco ⍵}¨⍵}+/∘⍳¨⍵}⍳13000" "{{⍵/⍨500≤{×/1+⊢⌿2 pco ⍵}¨⍵}2÷⍨×⌿0 1∘.+⍵}⍳13000"
{{⍵/⍨500≤{×/1+⊢⌿2 pco ⍵}¨⍵}+/∘⍳¨⍵}⍳13000 → 7.7E¯1 | 0%
{{⍵/⍨500≤{×/1+⊢⌿2 pco ⍵}¨⍵}2÷⍨×⌿0 1∘.+⍵}⍳13000 → 7.0E¯1 | -9%
I thought that the specific formula would give much speed up...