1. 
   Hyperoperation
   [group theory] == Licensing: == ...
   Found op http://en.wikipedia.org/wiki/Hyperoperation_(group_theory)
   
   
2. 
   Hyperoperation
   Sequences similar to the hyperoperation sequence have historically been referred to by many names, including: the Ackermann function (3-argument), the Ackermann hierarchy, the Grzegorczyk hierarchy (which is more general), Goodstein`s version of the Ackermann function, operation of the nth grade, z...
   Found op http://en.wikipedia.org/wiki/Hyperoperation
   
   

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