Comment by omoikane
7 hours ago
A better title might have been "fastest growing function with 64bit arguments". The main value of this article is really the various functions that take larger strides to cover a finite range that's significantly larger than 2^64-1.
If it were about coding fast growing functions, then it would have had to mention the incredible 47-bit lambda calculus term λn. n n (λe λx. x e x) (λm. m (λe. m e m)) that achieves f_ε₀ growth. But it expects its argument to be a so-called state numeral n, rather than a Church numeral, and even state numeral 2, which is \e\f\x.f e (\e.f e x) is already 32 bits long, making the application take 2+47+32=81 bits, more than the required 64.