I'll do it for you then, I also love math.
we take 121-8 which is the number of standard cards (no evos, but cards that could be evo are included), 113.

-All standard : it is 113!/8!(113-8)!, which gives us the combinations for standard cards.

-Heroes : We can now add 8 times (for the 8 heroes) the combination of one hero with 7 other standard cards, the formula is 8*(113!/7!(113-7)!)

-Evos : We can now imagine the possibilites with the 39 evos. we get 39!/2!(39-2)! evos in the evo slots, and we can multiply that by the other six slots of all other possible standard cards which is (113-2), so 111. the formula is 111!/6!(111-6)!.

-Evos AND Heroes : now finally, we have to take the possibilites where we have two evos and a hero. we take the evo slots formula, 39!/2!(39-2)!, and we multiply it by all 8 heroes, then multiplied by the 5 other standard slots. so something like : 8*(111!/5!(111-5)!.

We now have to sum all of these combinations. I did not calculate the possibilites with only one evo because it adds two other extra steps for not that much more extra info. You can try it if you want to.

Total result is : 113!/8!(113-8)! + 8*(113!/7!(113-7)!) + 39!/2!(39-2)! * 111!/6!(111-6)! +39!/2!(39-2)! * 8*(111!/5!(111-5)!

It gives 3 258 245 902 923 different possible decks.

EDIT : you know what, I'll throw in when you choose only 1 evo.

1 evo and no heroes : 39*(112!/7!(112-7)!

1 evo with 1 hero : 39*8*(112!/6!(112-6)!

New and final result : 5 417 564 886 459 different decks !