Using triangles to calculate perfect squares in Racket

perfect-squares-tri.rkt

#lang racket

(define (get-triangle row)
  (cond 
    ( ( = row 0) 0)
    ( ( = row 1) 1)
    ( else (+ row (get-triangle (sub1 row))  ))))

(define (nth-perfect-square count)
  (cond 
    ( (= count 1 ) 1)
    ( else  (+ (get-triangle (sub1 count)) (get-triangle count)) )))

(get-triangle 1)
(get-triangle 2)
(get-triangle 3)

(nth-perfect-square 1)
(nth-perfect-square 2)
(nth-perfect-square 3)
(nth-perfect-square 4)
(nth-perfect-square 5)