|
|
A296880
|
|
Numbers whose base-9 digits d(m), d(m-1), ..., d(0) have #(pits) > #(peaks); see Comments.
|
|
4
|
|
|
82, 83, 84, 85, 86, 87, 88, 89, 163, 164, 165, 166, 167, 168, 169, 170, 173, 174, 175, 176, 177, 178, 179, 244, 245, 246, 247, 248, 249, 250, 251, 254, 255, 256, 257, 258, 259, 260, 264, 265, 266, 267, 268, 269, 325, 326, 327, 328, 329, 330, 331, 332, 335
(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
|
|
|
EXAMPLE
|
The base-9 digits of 335 are 4,1,2; here #(pits) = 1 and #(peaks) = 0, so 335 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
|
|
|
KEYWORD
|
nonn,base,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|