User blog comment:MemoryAngel/Hashtags and E's?/@comment-11227630-20170927155600

And more about common notations on this wiki: Maybe I lost many other notations.
 * Superscripts mean exponentiation or functional iteration;
 * Left superscripts mean tetration;
 * a!b mainly means hyperfactorial array notation;
 * G means G function, Goodstein function, Graham's number or its sequence;
 * g means Graham's function, Ackermann's Generalized Exponential Notation, weak Goodstein function or slow-growing hierarchy;
 * f mainly means fast-growing hierarchy;
 * H means Hardy hierarchy, Chris Bird's H function or SuperJedi224's H* function;
 * ↑ means arrow notation;
 * Multiple ^'s mean arrow notation;
 * → means Chained arrow notation;
 * A mainly means Ackermann function;
 * means Jonathan Bowers' extended operators;
 * {} means BEAF (using as separators) or Bird's array notation (using [] as separators);
 * [] means Steinhaus-Moser Notation, copy notation, separator of Bird's array notation, Graham Array Notation, arrays of Username5243's Array Notation or hyperfactorial array notation.