chickadee » math » square-number?

triangle-number? nprocedure
square-number? nprocedure
pentagonal-number? nprocedure
hexagonal-number? nprocedure
heptagonal-number? nprocedure
octagonal-number? nprocedure
n
integer

These functions check whether the input is a polygonal number of the types triangle, square, pentagonal, hexagonal, heptagonal and octogonal respectively.

Wikipedia: Polygonal Number