a_\anglnThe notation 'a_\angln' is used to denote an annotated variable 'a' with a subscript 'n' that is often used to indicate a specific element in a sequence or a series. The 'angle' symbol is typically used to provide additional context or annotation to the variable, which can be useful in mathematical proofs or explanations where specific elements need to be highlighted or differentiated from others.
Annotated element of a sequence representing the nth term as the reciprocal of n.
a_\angln = \frac{1}{n}Annotated element of a sequence representing a quadratic expression for the nth term.
a_\angln = n^2 + 3n + 2Annotated element of a sequence representing the sine of an angle multiplied by n.
a_\angln = \sin(n\theta)