User blog comment:Mh314159/new YIP notation/@comment-39585023-20190706235552/@comment-35470197-20190707010358

The computation of \([1]\) terminates because you have \([a] = f_{[a-1]}^{[a-1]}(a)\). Namely, you have \([1] = f_{[0]}^{[0]}(1) = f_1^1(1) = f_0(2) = 3\).