18 lines
446 B
Text
18 lines
446 B
Text
# If n is non-negative, then A002487(n)
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# generates an array with at least n elements of
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# the A002487 sequence;
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# if n is negative, elements are added until (-n)
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# is found.
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def A002487(n):
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[0,1]
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| until(
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length as $l
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| if n >= 0 then $l >= n
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else .[$l-1] == -n
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end;
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length as $l
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| ($l / 2) as $n
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| .[$l] = .[$n]
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| if (.[$l-2] == -n) then .
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else .[$l + 1] = .[$n] + .[$n+1]
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end ) ;
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