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A301516
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Numbers n with decimal expansion (d_1, ..., d_k) such that the convex hull of the set of points { (i, d_i), i = 1..k } has positive area.
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2
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100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 148, 149, 150, 151, 152, 153, 154, 155
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internal format)
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OFFSET
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1,1
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COMMENTS
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This sequence is the complement of the straight-line numbers (0..99 alongside A135643).
This sequence first differs from A134999 at n = 857: a(857) = 1001 whereas A134999(857) = 1011.
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LINKS
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PROG
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(PARI) is(n, base=10) = my (d=digits(n, base)); for (i=1, #d-2, if (d[i]+d[i+2]-2*d[i+1], return (1))); return (0)
(Python)
def ok(n):
d = list(map(int, str(n)))
return any(d[i]+d[i+2]-2*d[i+1] != 0 for i in range(len(d)-2))
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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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