=	{1, 2, 3, . . . }
	=	{1, 2, 3, . . . , k}
(AP)	:	Addition Principle
(MP)	:	Multiplication Principle
(CP)	:	Complementation Principle
(IP)	:	Injection Principle
(BP)	:	Bijection Principle
(PP)	:	Pigeonhole Principle
(GPP)	:	Generalised Pigeonhole Principle
(PIE)	:	Principle of Inclusion and Exclusion
(GPIE)	:	Generalised Principle of Inclusion and Exclusion
(BT)	:	Binomial Theorem
LHS	:	Left-hand side
RHS	:	Right-hand side
|S|	=	the number of elements in the set S
	=	the largest integer less than or equal to x
	=	the largest integer less than or equal to x
FTA	:	Fundamental Theorem of Arithmetic
gcd	:	greatest common divisor
Bn	=	Bell number
	=	the number of ways of dividing n distinct objects into (nonempty) groups
C(n)	=	Catalannumber
	=	the number of shortest routes from O(0, 0) to A(n, n) which do not cross the diagonal y = x in the rectangular coordinate system
Dn	=	the number of derangements of
s*(m, k)	=	the number of ways of arranging m distinct objects around k identical circles such that each circle has at least one object
s(m, k)	=	Stirling number of the first kind
	=	the coefficient of xk in the expansion of x(x – 1)(x – 2) … (x – (m – 1))
S(m, k)	=	Stirling number of the second kind
	=	the number of ways of distributing m distinct objects into k identical boxes such that no box is empty
	=	the number of r-element subsets of an n-element set
Pnr	=	the number of r-permutations of n distinct objects
AIME	:	American Invitational Mathematics Examination