

A296891


Numbers whose base13 digits d(m), d(m1), ..., 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
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OFFSET

1,2


COMMENTS

A pit is an index i such that d(i1) > d(i) < d(i+1); a peak is an index i such that d(i1) < d(i) > d(i+1). The sequences A296891A296894 partition the natural numbers. See the guides at A296712 and A296882.


LINKS



EXAMPLE

The base13 digits of 2550 are 1,2,1,2; here #(pits) = 1 and #(peaks) = 1, so 2550 is in the sequence.


MATHEMATICA

z = 200; b = 13;
d[n_] := Differences[Sign[Differences[IntegerDigits[n, b]]]];
Select[Range [z], Count[d[#], 2] == Count[d[#], 2] &] (* A296891 *)
Select[Range [z], Count[d[#], 2] < Count[d[#], 2] &] (* A296892 *)
Select[Range [z], Count[d[#], 2] > Count[d[#], 2] &] (* A296893 *)


CROSSREFS



KEYWORD

nonn,base,easy


AUTHOR



STATUS

approved



