Y  =. ]:&>/]:^:_1 b.]:`(<'0';_1)`:6&([ 128!:2 ,&<)
   sr =. [ apply f. ,&<   NB. Self referring
   fac=. 1:`(] * [ sr ] - 1:)@.(0 < ])
   fib=. (([ sr ] - 2:) + [ sr ] - 1:)^:(1 < ])