User blog comment:Deedlit11/Ordinal notations II: Up to the Bachmann-Howard ordinal/@comment-1605058-20130629142358

If we take fundamental sequence (w^2)[n] we have w^(2[0])*n. But 2 is successor, so it doesn't have fundamental sequence. I believe good formula in that case is w^(a+1)[n]=w^a*n.