My attempt to steal is about 39%.

I had AJo when I open raised in the Cut-Off the other day against an aggressive player that resteals 23% in total over a reasonable sample of about 160 resteal opportunities, although he may resteal less against the Cut-Off than against the Button and Small Blind of course.

We were both 100bb's deep, I'd opened to 2.5x and they 3bet to 9x.

I decided to 4bet to 19x and then called the player's jam, even though we have no real history that I can remember.

Was my play mathematically correct?

what is his 5bet range, Pokie?

either way, unless he's 3bet/5betting a larger portion of his resteal range then its likely going to be better to flat the 3bet to keep in all the junk in his resteal range that AJ is ahead of.

This is a pretty straightforward EV problem but generally my take:

4bet/call AKo is completely standard. However, there are plenty of nits at micro stakes against which its a bad play. Against an average player (at micros) its borderline and IMO overused.

4bet/call AQo is dubious. On average I think its a bad play, but certainly has some use against some players.

4bet/call AJo is really stretching it. I'd make this play extremely rarely and only against true maniacs.

I came across this chart online. Is it mathematically correct?

Opponent's 3-bet Percentage Required to 4-bet/call off preflop for 100bb's.
* KK+: Good against any range
* QQ: vs 3% or higher
* JJ: vs 6.5% or higher
* TT: vs 8.5% or higher
* 99: vs 10.5% or higher
* 88: vs 12.5% or higher
* 77: vs 14% or higher
* AKs: vs 3% or higher
* AQs: vs 8% or higher
* AJs: vs 13% or higher
* AKo: vs 5% or higher
* AQo: vs 9% or higher

I have AJo which according to the chart, means I should be able to 4bet/call against a 3bet range of 16%+, (looking at AJs, it says you need 13% only, so AJo perhaps a pinch more).

However, I did some calculations myself and I dispute this personally, and I think I made an error here when stacking off AJo vs this opponent in the above hand.

those percentage must be his 3bet/shoving range..not just 3beting range. there are plenty of people 3beting 12%, but their stackoff range (3bet/shoving) is no more than 2,5% (only monsters).

if you have small sample on villain, then i guess its fold with AJo against 3bet (i would call AJs). if you have big enough sample and you know he could fold to 4bet, then its 4bet/fold.