User blog comment:Rpakr/A Formal Definition of Pair Sequence System using BM1 Rules/@comment-35470197-20180814221408/@comment-32697988-20180814221628

In 2.3 it is Pair(nonnegative integer, nonnegative integer) and in 2.14 it is Pair(natural,sequence) so it is technically not multiply defined. However, I do agree that it is confusing so maybe I will change at least one of them.