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A296869 Numbers whose base-5 digits d(m), d(m-1), ..., d(0) have #(pits) < #(peaks); see Comments. 4
35, 36, 40, 41, 42, 45, 46, 47, 48, 65, 66, 67, 70, 71, 72, 73, 95, 96, 97, 98, 160, 161, 165, 166, 167, 170, 171, 172, 173, 175, 180, 181, 190, 191, 192, 195, 196, 197, 198, 200, 205, 206, 210, 211, 212, 220, 221, 222, 223, 225, 230, 231, 235, 236, 237, 240 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
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 A296867-A296869 partition the natural numbers. See the guides at A296882 and A296712.
LINKS
EXAMPLE
The base-5 digits of 240 are 1,4,3,0; here #(pits) = 0 and #(peaks) = 1, so 240 is in the sequence.
MATHEMATICA
z = 200; b = 5;
d[n_] := Differences[Sign[Differences[IntegerDigits[n, b]]]];
Select[Range [z], Count[d[#], -2] == Count[d[#], 2] &] (* A296867 *)
Select[Range [z], Count[d[#], -2] < Count[d[#], 2] &] (* A296868 *)
Select[Range [z], Count[d[#], -2] > Count[d[#], 2] &] (* A296869 *)
updnQ[n_]:=Total[Which[#[[1]]<#[[2]]>#[[3]], 1, #[[1]]>#[[2]]<#[[3]], -1, True, 0]&/@Partition[IntegerDigits[n, 5], 3, 1]]>0; Select[Range[ 250], updnQ] (* Harvey P. Dale, Dec 20 2020 *)
CROSSREFS
Sequence in context: A210320 A165856 A319484 * A099647 A064993 A041611
KEYWORD
nonn,base,easy
AUTHOR
Clark Kimberling, Jan 09 2018
STATUS
approved

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Last modified April 19 23:40 EDT 2024. Contains 371798 sequences. (Running on oeis4.)