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A296881 Numbers n whose base-9 digits d(m), d(m-1), ..., d(0) have #(pits) < #(peaks); see Comments. 3
99, 100, 108, 109, 110, 117, 118, 119, 120, 126, 127, 128, 129, 130, 135, 136, 137, 138, 139, 140, 144, 145, 146, 147, 148, 149, 150, 153, 154, 155, 156, 157, 158, 159, 160, 189, 190, 191, 198, 199, 200, 201, 207, 208, 209, 210, 211, 216, 217, 218, 219, 220 (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 A296879-A296881 partition the natural numbers. See the guides at A296882 and A296712.

LINKS

Clark Kimberling, Table of n, a(n) for n = 1..10000

EXAMPLE

The base-9 digits of 220 are 2,6,4; here #(pits) = 0 and #(peaks) = 1, so that 220 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

Cf. A296882, A296712, A296879, A296880.

Sequence in context: A305359 A213157 A317592 * A243259 A171904 A171903

Adjacent sequences:  A296878 A296879 A296880 * A296882 A296883 A296884

KEYWORD

nonn,base,easy

AUTHOR

Clark Kimberling, Jan 10 2018

STATUS

approved

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Last modified April 5 03:58 EDT 2020. Contains 333238 sequences. (Running on oeis4.)