User blog comment:Deedlit11/Ordinal Notations V: Up to a weakly Mahlo cardinal/@comment-24509095-20140509071457/@comment-5150073-20140510154929

Wait, really. We can define then \chi(M,1)[n] = $$\chi(\chi(M)[n],\chi(M)+1)$$, but we have dissimilarity with $$\vartheta$$ function then.