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A296864 Numbers whose base-4 digits d(m), d(m-1), ..., d(0) have #(pits) = #(peaks); see Comments. 4
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 20, 21, 22, 23, 26, 27, 31, 32, 36, 37, 40, 41, 42, 43, 47, 48, 52, 53, 56, 57, 58, 60, 61, 62, 63, 64, 65, 66, 67, 68, 72, 73, 76, 77, 78, 80, 84, 85, 86, 87, 90, 91, 95, 97, 98, 99, 102, 103, 104, 105 (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 A296864-A296866 partition the natural numbers. See the guides at A296882 and A296712.
LINKS
EXAMPLE
The base-4 digits of 105 are 1, 2, 2, 1; here #(pits) = 0 and #(peaks) = 0, so 105 is in the sequence.
MATHEMATICA
z = 200; b = 4;
d[n_] := Differences[Sign[Differences[IntegerDigits[n, b]]]];
Select[Range [z], Count[d[#], -2] == Count[d[#], 2] &] (* A296864 *)
Select[Range [z], Count[d[#], -2] < Count[d[#], 2] &] (* A296865 *)
Select[Range [z], Count[d[#], -2] > Count[d[#], 2] &] (* A296866 *)
CROSSREFS
Sequence in context: A017909 A345201 A316530 * A124695 A005555 A128829
KEYWORD
nonn,base,easy
AUTHOR
Clark Kimberling, Jan 09 2018
STATUS
approved

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Last modified June 21 19:23 EDT 2024. Contains 373558 sequences. (Running on oeis4.)