<=19

B: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, ...

P: <3 <3 <3 <3 <3 <3 <3 X X X X X X X X X X X X X X ...

AB: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

20

B: 1, 2, 4, 8, 16, 32, 64, 128, 256, 1, 2, 4, 8, 16, 32, 64, 128, ...

P: <3 <3 <3 <3 <3 <3 <3 X X X X X X <3 <3 <3 <3 <3 <3 <3 <3 <3 ...

AB: - - - - - - - - - - - - - - - - - - - - - - ^ - - - - - - - - - - - - - - - - - - - 

21

B: 1, 2, 4, 8, 1, 2, 4, 1, 2, 4, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, ...

P: <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 X X X X X X X X X X X X X X X ...

AB: - - - - ^ - - - - ^ - - - - ^ - - - - - - - - - - - - - - - - ^ - - ^ - - ^ - - - ^ ^ ^ ^ ^ ^ ^ ^ ^ ^

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Original puzzle above. Hints will be put down here.

Hint 1:

> 
>  19th, 20th, 21st
> 
> 
> 

Hint 2:

> 
>  there is no math tag
> 
> 
> 

Hint 3:

> 
>  <3 means heart
> 
> 
>