查看“︁DO”︁的源代码

DO（Duchhart's Ordinal），是一个重要的[[序数]]。
{| class="wikitable"
![[序数记号]]
!表达式
|-
|[[OCF#BOCF|BOCF]]
|<math>\psi(\Omega_{\kappa+1})</math>
|-
|[[反射序数]]
|<math>\psi(2 \ \text{aft} \ 4)</math>
|-
|[[BMS]]
|<math>(0)(1,1,1)(2,1,1)(3,1,1)(4,1,1)(5,1)(6,2)</math>
|-
|[[0-Y]]
|<math>1,4,7,10,13,15,19</math>
|-
|[[Y序列|1-Y]]
|<math>1,2,4,8,12,16,20,23,27</math>
|-
|[[ex-hydra]]
|<math>p1(p3(p3(p3(p3(p2(p3))))))</math>
|-
|[[Dropping#M 记号|M 记号]]
|<math>p(p(M^{M^{M^M}}+M))</math>
|-
|[[投影序数|投影]]
|<math>\psi(\psi_\alpha(\Omega_{\alpha+1}^{\Omega_{\alpha+1}^{\Omega_{\alpha+1}^{\varepsilon_{\alpha+1}}}}))</math>
|}

=== 性质 ===
[[证明论序数]]：<math>\rm KP+\Pi_4-Reflection</math>

极限在此处的记号：Duchhart's OCF
[[分类:序数]]