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A296904
Numbers whose base-20 digits d(m), d(m-1), ..., d(0) have #(pits) > #(peaks); see Comments.
4
401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 801, 802, 803, 804, 805, 806, 807, 808, 809, 810, 811, 812, 813, 814, 815, 816, 817, 818, 819, 822, 823, 824, 825, 826, 827, 828, 829, 830, 831, 832, 833, 834, 835
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 A296903..A296905 partition the natural numbers. See the guides at A296712 and A296882.
LINKS
EXAMPLE
The base-20 digits of 328822 are 2,1,2,1,2; here #(pits) = 2 and #(peaks) = 1, so 328822 is in the sequence.
MATHEMATICA
z = 200; b = 20;
d[n_] := Differences[Sign[Differences[IntegerDigits[n, b]]]];
Select[Range [z], Count[d[#], -2] == Count[d[#], 2] &] (* A296903 *)
Select[Range [z], Count[d[#], -2] < Count[d[#], 2] &] (* A296904 *)
Select[Range [z], Count[d[#], -2] > Count[d[#], 2] &] (* A296905 *)
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Clark Kimberling, Jan 12 2018
STATUS
approved