User blog:Wythagoras/Very strong variant of BEAF

The & operator works as in Ikosarakts definition

The first difference is in the legions.

\({X,X/1/1.../1/1/n/\#}&k\) = \(\{X,X/1/1.../1/\{X,X/1/1.../1/\{X,X/1/1.../1/\{...\}&X/n-1/\#\}&X/n-1/\#\}&X/n-1/\#\}&k\)