Annuity and factorial notation

Actuarial mathematics makes frequent use of a notation that as far as I know isn't used anywhere else, and that is a bracket enclosing the northeast corner of a symbol.

This is used as subscript of another symbol, such as ana or ans, and there may be other decorations such more superscripts or subscripts.

For typesetting in LaTeX, the bracket is the only part that's not standard. If you can put a bracket around a symbol, you can make the bracketed symbol a subscript just as you'd make anything else a subscript. LaTeX package actuarialangle lets you do this.

The angle notation that actuaries use for annuity-related calculations is not used anywhere else that I know of, but a variation was once used for factorials back in the 1800s, putting a bracket around the southwest corner of a symbol rather than the northeast. You can see examples here, including one use by David Hilbert.

Related post: Floor, ceiling, bracket

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