User blog comment:Alemagno12/DAN is weaker than R function/@comment-11227630-20170827073324

{1,,,1{1,,,1,,,2}2} is valid.

s(n,n{1,,,1,,,2}2) runs into the adding case, and s(n,n{1,,,1,,,2}2) = s(n,n{1,,,1{1,,,1,,,2}2}2).

s(n,n{1,,,1{1,,,1,,,2}2}2) runs into the adding case, and s(n,n{1,,,1{1,,,1,,,2}2}2) = s(n,n{1,,,1{1,,,1{1,,,1,,,2}2}2}2).

s(n,n{1,,,1{1,,,1{1,,,1,,,2}2}2}2) runs into the expanding case, and s(n,n{1,,,1{1,,,1{1,,,1,,,2}2}2}2) = s(n,n{1,,,1{1,,,1...{1,,,1{1,,,1,2}2}...2}2}2).

So there's no loop here.