20 lines
468 B
Common Lisp
20 lines
468 B
Common Lisp
; generate the sequence and check GCD
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(for ((n 10000))
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(unless (= (gcd (stern n) (stern (1+ n))) 1) (error "BAD GCD" n)))
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→ #t
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;; first items
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(define sterns (cache 'stern))
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(subvector sterns 1 16)
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→ #( 1 1 2 1 3 2 3 1 4 3 5 2 5 3 4)
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;; first occurences index
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(for ((i (in-range 1 11))) (write (vector-index i sterns)))
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→ 0 3 5 9 11 33 19 21 35 39
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;; 100
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(writeln (vector-index 100 sterns))
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→ 1179
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(stern 900000) → 446
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(stern 900001) → 2479
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