User blog comment:Kyodaisuu/Mashimo function/@comment-5150073-20140706180008/@comment-24061664-20140707142430

H, V, L, D are obvious. BH is from Bachmann-Howard, O is from Omega, OF is from omega fixed point. I think these functions are not so often used outside the definition of M(n) function, and therefore not so confusing. Out of these, H function may be a little bit interesting.

CKF is from Church Kleene Fixed point - because \(alpha mapsto \omega_\alpha^{CK}\) is similar to omega fixed point. FC is FGH + CKF, RC is Rayo + CKF. At first I wrote FCK and RCK, but as FCK looks like F*CK, I made them 2 letters.