15 lines
462 B
Racket
15 lines
462 B
Racket
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#lang racket
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(require math/number-theory)
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(define (sum-of-digits n (σ 0))
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(if (zero? n) σ (let-values (((q r) (quotient/remainder n 10)))
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(sum-of-digits q (+ σ r)))))
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(define (additive-prime? n)
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(and (prime? n) (prime? (sum-of-digits n))))
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(define additive-primes<500 (filter additive-prime? (range 1 500)))
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(printf "There are ~a additive primes < 500~%" (length additive-primes<500))
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(printf "They are: ~a~%" additive-primes<500)
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