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

%I A296881 #7 Jan 21 2023 18:04:55
%S A296881 99,100,108,109,110,117,118,119,120,126,127,128,129,130,135,136,137,
%T A296881 138,139,140,144,145,146,147,148,149,150,153,154,155,156,157,158,159,
%U A296881 160,189,190,191,198,199,200,201,207,208,209,210,211,216,217,218,219,220
%N A296881 Numbers whose base-9 digits d(m), d(m-1), ..., d(0) have #(pits) < #(peaks); see Comments.
%C A296881 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.
%H A296881 Clark Kimberling, <a href="/A296881/b296881.txt">Table of n, a(n) for n = 1..10000</a>
%e A296881 The base-9 digits of 220 are 2,6,4; here #(pits) = 0 and #(peaks) = 1, so 220 is in the sequence.
%t A296881 z = 200; b = 9;
%t A296881 d[n_] := Differences[Sign[Differences[IntegerDigits[n, b]]]];
%t A296881 Select[Range [z], Count[d[#], -2] == Count[d[#], 2] &]  (* A296879 *)
%t A296881 Select[Range [z], Count[d[#], -2] < Count[d[#], 2] &]   (* A296880 *)
%t A296881 Select[Range [z], Count[d[#], -2] > Count[d[#], 2] &]   (* A296881 *)
%Y A296881 Cf. A296882, A296712, A296879, A296880.
%K A296881 nonn,base,easy
%O A296881 1,1
%A A296881 _Clark Kimberling_, Jan 10 2018