See note on graphs


See also topology

Rational Tangles - infinite series


See also abstract algebra

“where greedy works”



Circle packing. Really cool. A discrete analog of complex functions



Generating function generatingfunctionology combinatorial species

Shadow calculus Sums

Concrete mathematics

PIE principle inlcusion exclusion

pigeon hole principle The continuous analog.

polya enumeration theorem polya’s theory of counting

handbook of combinatorics

Finite geometry

Ramsey Theory

Big step up in sophistication huh Principles that

Cody says has something to do with well quasi-orders Schur number 5 = 161. 2017

Ramsey number solution to party problem. R(m,n) m know each other or n don’t know each other. Diagonal vs nondiagonal 2023 breakthrough on upper bound


See lik the whole pile on logic

Set theory


Order Theory Finite po-sets visualizing posets

-- an attempt
class PartialOrder (A : Type) (R : A -> A -> Prop) where
  refl : forall x, R x x
  antisym : forall x y, R x y -> R y x -> x = y
  trans : forall x y z, R x y -> R y z -> R x z

instance : PartialOrder Nat Eq where 
  refl := fun x => by rfl
  antisym := fun x y r1 _r2 => by rw [r1]
  trans := fun x y z r1 r2 => by rw [r1, r2]

def main := IO.println "hello world"


See also abstract algebra