A296881 Numbers whose base-9 digits d(m), d(m-1), ..., d(0) have #(pits) < #(peaks); see Comments.

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

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 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