Brazilian numbers: Difference between revisions
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First 20 prime Brazilians:
[7,13,31,43,73,127,157,211,241,307,421,463,601,757,1093,1123,1483,1723,2551,2801]</pre>
=={{header|Racket}}==
<lang racket>#lang racket
(require math/number-theory)
(define (repeat-digit? n base d-must-be-1?)
(call-with-values
(λ () (quotient/remainder n base))
(λ (q d) (and (or (not d-must-be-1?) (= d 1))
(let loop ((n q))
(if (zero? n)
d
(call-with-values
(λ () (quotient/remainder n base))
(λ (q r) (and (= d r) (loop q))))))))))
(define (brazilian? n (for-prime? #f))
(for/first ((b (in-range 2 (sub1 n))) #:when (repeat-digit? n b for-prime?)) b))
(define (prime-brazilian? n)
(and (prime? n) (brazilian? n #t)))
(module+ main
(displayln "First 20 Brazilian numbers:")
(stream->list (stream-take (stream-filter brazilian? (in-naturals)) 20))
(displayln "First 20 odd Brazilian numbers:")
(stream->list (stream-take (stream-filter brazilian? (stream-filter odd? (in-naturals))) 20))
(displayln "First 20 prime Brazilian numbers:")
(stream->list (stream-take (stream-filter prime-brazilian? (stream-filter odd? (in-naturals))) 20)))</lang>
{{out}}
<pre>First 20 Brazilian numbers:
'(7 8 10 12 13 14 15 16 18 20 21 22 24 26 27 28 30 31 32 33)
First 20 odd Brazilian numbers:
'(7 13 15 21 27 31 33 35 39 43 45 51 55 57 63 65 69 73 75 77)
First 20 prime Brazilian numbers:
'(7 13 31 43 73 127 157 211 241 307 421 463 601 757 1093 1123 1483 1723 2551 2801)</pre>
=={{header|Raku}}==
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