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A296905
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Numbers whose base-20 digits d(m), d(m-1), ..., d(0) have #(pits) < #(peaks); see Comments.
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4
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440, 441, 460, 461, 462, 480, 481, 482, 483, 500, 501, 502, 503, 504, 520, 521, 522, 523, 524, 525, 540, 541, 542, 543, 544, 545, 546, 560, 561, 562, 563, 564, 565, 566, 567, 580, 581, 582, 583, 584, 585, 586, 587, 588, 600, 601, 602, 603, 604, 605, 606, 607
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OFFSET
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1,1
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COMMENTS
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A pit is an index i such that d(i-1) > d(i) < d(i+1); a peak is an index i such that d(i-1) < d(i) > d(i+1). The sequences A296903..A296905 partition the natural numbers. See the guides at A296712 and A296882.
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LINKS
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EXAMPLE
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The base-20 digits of 176441 are 1,2,1,2,1; here #(pits) = 1 and #(peaks) = 2, so 176441 is in the sequence.
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MATHEMATICA
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z = 200; b = 20;
d[n_] := Differences[Sign[Differences[IntegerDigits[n, b]]]];
Select[Range [z], Count[d[#], -2] == Count[d[#], 2] &] (* A296903 *)
Select[Range [z], Count[d[#], -2] < Count[d[#], 2] &] (* A296904 *)
Select[Range [z], Count[d[#], -2] > Count[d[#], 2] &] (* A296905 *)
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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