Some streaming services may have modified or added episodes that disturb the numbering sequence.
I am watching on Disney+, and just noticed on Season 6. Here, Episode 1 is Blue Harvest, but on Disney it's Episode 1&2, so that throws the numbering off by 1 until you get to E10, Play It Again Brian, which is on Disney as Episode 11.
Then, Disney has an unlisted Episode 12, 100th Episode Special.
Their Episode 13, Former Life Of Brian is listed here as E11, and their E14, Long John Peter is listed here as 12.
The unlisted Special throws the remaining numbering off by 2.
Season 8 on Disney has Episode 20 & 21 as two parts of the listed E20, Something, Something, Something Dark Side, while the listed E21, Partial Terms of Endearment does not show up on Disney at all.
In Season 9, e1 And Then There Were Fewer is 2 episodes, e7 Road To The North Pole is 2 episodes, e18 It's A Trap is also two episodes, on Disney+ as e20 and e21.
Season 11 on Disney adds yet another special right after e4 Yug Ylimaf.
They have a 200 Episodes Later as e5, throwing of the whole season's numbering by 1.
Season 13, once again adds an Episode number by breaking Episode 1, The Simpsons Guy into two episodes, throwing everything off by 1.
Season 14 & 15 are okay, and that's as far as I've checked so far.
I am watching on Disney+, and just noticed on Season 6. Here, Episode 1 is Blue Harvest, but on Disney it's Episode 1&2, so that throws the numbering off by 1 until you get to E10, Play It Again Brian, which is on Disney as Episode 11.
Then, Disney has an unlisted Episode 12, 100th Episode Special.
Their Episode 13, Former Life Of Brian is listed here as E11, and their E14, Long John Peter is listed here as 12.
The unlisted Special throws the remaining numbering off by 2.
Season 8 on Disney has Episode 20 & 21 as two parts of the listed E20, Something, Something, Something Dark Side, while the listed E21, Partial Terms of Endearment does not show up on Disney at all.
In Season 9, e1 And Then There Were Fewer is 2 episodes, e7 Road To The North Pole is 2 episodes, e18 It's A Trap is also two episodes, on Disney+ as e20 and e21.
Season 11 on Disney adds yet another special right after e4 Yug Ylimaf.
They have a 200 Episodes Later as e5, throwing of the whole season's numbering by 1.
Season 13, once again adds an Episode number by breaking Episode 1, The Simpsons Guy into two episodes, throwing everything off by 1.
Season 14 & 15 are okay, and that's as far as I've checked so far.