IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html
At:
permute sum n:, f:(n), p:(nn).
Bij(n; n; p) sum(f(p(x)) | x < n) = sum(f(x) | x < n)
By:
Auto
THEN
FwdThru
Thm*k:, p:(kk). Bij(k; k; p) (L:(k-1) List. p = compose_flips(L))
[-1]
THEN
ExRepD
THEN
HypSubst -1 0
THEN
AllHyps Thin