IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html
At:
firstn map221 1. f : TopTop
2. n : 3. 0<n 4. l:Top List. firstn(n-1;map(f;l)) ~ map(f;firstn(n-1;l))
5. Top List
6. u : Top
7. v : Top List
8. firstn(n;map(f;v)) ~ map(f;firstn(n;v))
9. 0<n [(f(u)) / firstn(n-1;map(f;v))] ~ map(f;[u / firstn(n-1;v)])