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A296867 Numbers whose base-5 digits d(m), d(m-1), ..., d(0) have #(pits) = #(peaks); see Comments. 4

%I #7 Jan 22 2023 20:51:06

%S 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,30,

%T 31,32,33,34,37,38,39,43,44,49,50,55,56,60,61,62,63,64,68,69,74,75,80,

%U 81,85,86,87,90,91,92,93,94,99,100,105,106,110,111,112

%N Numbers whose base-5 digits d(m), d(m-1), ..., d(0) have #(pits) = #(peaks); see Comments.

%C 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.

%H Clark Kimberling, <a href="/A296867/b296867.txt">Table of n, a(n) for n = 1..9999</a>

%e The base-5 digits of 112 are 4,2,2; here #(pits) = 0 and #(peaks) = 0, so 112 is in the sequence.

%t z = 200; b = 5;

%t d[n_] := Differences[Sign[Differences[IntegerDigits[n, b]]]];

%t Select[Range [z], Count[d[#], -2] == Count[d[#], 2] &] (* A296867 *)

%t Select[Range [z], Count[d[#], -2] < Count[d[#], 2] &] (* A296868 *)

%t Select[Range [z], Count[d[#], -2] > Count[d[#], 2] &] (* A296869 *)

%Y Cf. A296882, A296712, A296868, A296869.

%K nonn,base,easy

%O 1,2

%A _Clark Kimberling_, Jan 09 2018

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Last modified June 19 15:09 EDT 2024. Contains 373503 sequences. (Running on oeis4.)