I made 10 attemps to beeline mathematics and build the HG last night (Aztecs, deity, standard pangaea, all standard settings).
Every single time some AI built it before turn 50.
My research path was mining > AH > archery> the wheel > math. Sometimes the HG was built before I had time to research math.
Once I had marble, and I got archery and masonry from ancient ruins, still no luck.
I think deity HG is highly unlikely.
Techs: Mining, Pottery Writing, AH, The wheel, Archery, Mathematics,Philosophy(NC & Legalism for free temple), Lux Tech, Civil Service(if rivers), -> Education ...
Build: Monument, Worker, Granary, Scout, Library, Water Mill(if river), Scout, Archer, HG
SC: Tradition Opener, 2 Liberty(free worker and worker speed), Aristocracy, ... Full Tradition (ideally saving Oligarchy for last // most games you will need Oligarchy after Aristocracy just to stay alive as going for HG attracts multiple early war decs... )
{this will cause your capital to grow tiles like wild fire - not uncommon to expand and grab luxuries - strategics 4 tiles away before turn 100...}
first 500 gold should go to a Cultured CS (will need mining resources to afford it early, mining luxuries have a secondary advantage of being prioritized by the governor when growing tiles and will save you some money from having to buy hills)
will need gold to buy some hills for mines ...
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Settle according to the 5,4 rule (5 production (8 turns monument, 14 turns worker) , 4 food (8 turn to grow to the second citizen))
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Acquire 2-3 +3 food tiles first (grassland, floodplain, wheat farms, cows, jungle bananas, Deer ) (grow grow grow)
Then 2-3 +3 production tiles (mines on hills) (will probably have to buy hills at this stage..)
Try to save some forests for chopping when building HG...
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With 6-7 pop you should be able to get HG done a bit after the 60 turn mark ...
Babylon can tech to Math faster (with settled GS from writing)..
Korea can also get to Math a bit faster by using 6-7 unemployed citizens to tech Math while building a settler ....
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The biggest problem however are the early war decs that will at best cause delays by occupying crucial production tiles ....
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Marble is not so great because you will usually research masonry after philosophy -> will be useful for NationalColege, HagiaSophia, NotreDame - not for the HG ...
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Another possible way might involve getting the GL(very very dicey on deity) and using it to bulb math ...I suspect low chances of success
(even with early culture ruins, french, and ideal (mining luxuries,hill, forested map) ...)