You can do super dense mathematical code in the ancient APL programming language[1]. I wonder how even more tiny this program could get at the hands of an APL expert if any still exist.

Here are some complete APL programs[2] to give a flavor of just how dense it can get:

Sum integers from 1 to 100:

  +/ι100

Find all primes from 2 to a given number R:

  (∼R∈R◦.×R)/R←1↓ιR

Play Conway's Game of Life:

  life←{↑1 ⍵∨.∧3 4=+/,¯1 0 1∘.⊖¯1 0 1∘.⌽⊂⍵}

[1] https://en.wikipedia.org/wiki/APL_%28programming_language%29

[2] http://www.vaxman.de/publications/apl_slides.pdf