Please excuse me, that does work. Here's one that hangs up:
EULER196←{+/(5(⍵+2)↑⊃C∧∨/∨⌿D∘.⊖D⌽¨C∧3≤+/+⌿D∘.⊖
(D←¯1 0 1)⌽¨C←⊂6(⍵+3)↑5(⍵+2)⍴,2=+⌿0=(⍳¯1↑,B)∘.|,B)[3;]
/(B←⊃(+/⊃⍳¨¯5↑(0≤A-1)/A-1)+⍳¨¯5↑(0≤A)/A←¯2 ¯1 0 1 2+⍵)[3;]}
(That's one line.)
It's probably poorly optimised, but it might as well be for its purpose here.
EULER196 8 works well, with 80 it takes a second or so, but 800 stalls,
and ^C (or ^C^C) doesn't seem to work.
So if you try EULER196 ⍣≡ 2, it will stall, but not because of ⍣≡.
My platform is 64-bit Mac OS X 10.10.5, on a Mid 2009 MacBook Pro.
Best regards,
⊣Louis
