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A322629
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For a nonnegative number m with decimal digits (d_1, ..., d_k), let s(m) be the area of the convex hull of the set of points { (i, d_i), i = 1..k }; a(n) = 2 * s(n).
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1
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1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 3, 2, 1, 0, 1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 7, 6, 5, 4, 3, 2, 1, 0, 1, 2, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 15, 14, 13
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OFFSET
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100,2
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COMMENTS
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The data section starts at offset 100, however the sequence is well-defined for smaller values of n: a(n) = 0 for n = 0...99.
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LINKS
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FORMULA
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A302907(n) = a(prime(n)) where n denotes the n-th prime number.
a(10^n) = n-1 for any n > 0.
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EXAMPLE
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For n = 1212:
- the corresponding convex hull is as follows:
(2,2) +-----+ (4,2)
/ /
/ /
(1,1) +-----+ (3,1)
- it has area 2, hence a(1212) = 4.
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PROG
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(PARI) See Links section.
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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