Find squares n where n+1 is prime: Difference between revisions

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=={{header|Racket}}==

<syntaxhighlight lang="racket">

#lang racket

(require racket)

(define (find-subprime-squares up-to)

(let rc ([curr-num 1]

[found '()])

(let ([n-sq (* curr-num curr-num)])

(cond [(>= n-sq up-to) (reverse found)]

[(prime? (add1 n-sq)) (rc (add1 curr-num) (cons n-sq found))]

[else (rc (add1 curr-num) found)]))))

(define (prime? n)

(let iter ([counter 2])

(cond [(eq? n 1) #f]

[(<= (expt counter 2) n)

(if (zero? (remainder n counter))

#f

(iter (add1 counter)))]

[else #t])))

(find-subprime-squares 1000)

</syntaxhighlight>

{{out}}

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'(1 4 16 36 100 196 256 400 576 676)