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A296879 Numbers whose base-9 digits d(m), d(m-1), ..., d(0) have #(pits) = #(peaks); see Comments. 5
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
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 A296879-A296881 partition the natural numbers. See the guides at A296882 and A296712.
LINKS
EXAMPLE
The base-9 digits of 67 are 7,4; here #(pits) = 0 and #(peaks) = 0, so 67 is in the sequence.
MATHEMATICA
z = 200; b = 9;
d[n_] := Differences[Sign[Differences[IntegerDigits[n, b]]]];
Select[Range [z], Count[d[#], -2] == Count[d[#], 2] &] (* A296879 *)
Select[Range [z], Count[d[#], -2] < Count[d[#], 2] &] (* A296880 *)
Select[Range [z], Count[d[#], -2] > Count[d[#], 2] &] (* A296881 *)
CROSSREFS
Sequence in context: A258070 A258071 A266279 * A296882 A296885 A296888
KEYWORD
nonn,base,easy
AUTHOR
Clark Kimberling, Jan 09 2018
STATUS
approved

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Last modified June 16 11:31 EDT 2024. Contains 373429 sequences. (Running on oeis4.)