查看“︁SDO”︁的源代码

SDO（Small Dropping Ordinal），由Username5243命名<ref>https://googology.fandom.com/wiki/User:Username5243/Username%27s_OCF</ref>，指代原版[[UNOCF]]极限，同时也是[[Dropping Hydra|N-dropping]]和[[N-shifting]]模式的极限。
{| class="wikitable"
![[序数记号]]
!表达式
|-
|[[稳定序数]]
|<math>\psi(\lambda\alpha.\Omega_{\alpha+\omega}-\Pi_0)</math>
|-
|[[投影序数]]
|<math>\psi(\psi_\alpha(\Omega_{\alpha+\omega}))</math>
|-
|[[投影序数|向上投影]]
|<math>\psi(\psi_S(\sigma S*2+\psi_{S_3}(\sigma S+1)))</math>
|-
|[[UNOCF]]
|<math>\psi(C(1\{\omega\}0)))</math>
|-
|[[BMS]]
|<math>(0)(1,1,1)(2,2,1)(3)</math>
|-
|[[0-Y]]
|<math>1,4,9,10</math>
|-
|[[Y序列|1-Y]]
|<math>1,2,4,8,15,16</math>
|-
|[[Ex-hydra]]
|<math>p1(p3(p5(p1))))</math>
|}

== 性质 ==
记号极限：[[SAN]]、[[R函数]]、[[Dropping Hydra]]等[[Dropping Hydra|N-dropping]]记号；[[TON]]主记号等[[N-shifting]]记号，[[UNOCF]]等多逗号模式记号，[[LPrSS Hydra]]
<references />