Factorial primes: Difference between revisions
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(Add Mathematica/Wolfram Language implementation) |
Rswalsh0509 (talk | contribs) (Added Common Lisp implementation without advanced primality testing.) |
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30: 469! - 1 = 67718096668149510900...99999999999999999999 (1051 digits) |
30: 469! - 1 = 67718096668149510900...99999999999999999999 (1051 digits) |
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31: 546! - 1 = 14130200926141832545...99999999999999999999 (1260 digits) |
31: 546! - 1 = 14130200926141832545...99999999999999999999 (1260 digits) |
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</pre> |
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=={{header|Common Lisp}}== |
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Simple implementation without using advanced primality testing. |
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<syntaxhighlight lang="lisp"> |
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(defun factorial (x) |
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(if (= x 1) |
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x |
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(* x (factorial (- x 1))))) |
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(defun is-factor (x y) |
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(zerop (mod x y))) |
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(defun is-prime (n) |
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(cond ((< n 4) (or (= n 2) (= n 3))) |
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((or (zerop (mod n 2)) (zerop (mod n 3))) nil) |
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(t (loop for i from 5 to (floor (sqrt n)) by 6 |
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never (or (is-factor n i) |
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(is-factor n (+ i 2))))))) |
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(defun main (&optional (limit 10)) |
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(let ((n 0) |
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(f 0)) |
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(loop while (< n limit) |
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for i from 1 |
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do (setf f (factorial i)) |
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(when (is-prime (+ f 1)) |
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(incf n) |
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(format t "~2d: ~2d! + 1 = ~12d~%" n i (+ f 1))) |
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(when (is-prime (- f 1)) |
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(incf n) |
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(format t "~2d: ~2d! - 1 = ~12d~%" n i (- f 1)))))) |
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</syntaxhighlight> |
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{{out}} |
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<pre> |
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1: 1! + 1 = 2 |
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2: 2! + 1 = 3 |
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3: 3! + 1 = 7 |
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4: 3! - 1 = 5 |
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5: 4! - 1 = 23 |
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6: 6! - 1 = 719 |
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7: 7! - 1 = 5039 |
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8: 11! + 1 = 39916801 |
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9: 12! - 1 = 479001599 |
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10: 14! - 1 = 87178291199 |
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</pre> |
</pre> |
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