# pentagonal(n) ? n
P ← ÷2×⊸(-1×3)
# is_pentagonal(n) ? n
IsP ← =⟜⌊°P

⧅<2 P+1⇡3000     # pentagonal number pairs
▽⊸(/(↧∩IsP⊃+-)⍉) # sum and diff are pent
/-⊢              # get first such (which is minimal)