This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A296873 #7 Jan 21 2023 18:05:30 %S A296873 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26, %T A296873 27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49, %U A296873 56,57,58,59,60,61,62,65,66,67,68,69,73,74,75,76,81,82 %N A296873 Numbers whose base-7 digits d(m), d(m-1), ..., d(0) have #(pits) = #(peaks); see Comments. %C A296873 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 A296873-A296875 partition the natural numbers. See the guides at A296882 and A296712. %H A296873 Clark Kimberling, <a href="/A296873/b296873.txt">Table of n, a(n) for n = 1..9999</a> %e A296873 The base-7 digits of 82 are 1,4,5; here #(pits) = 0 and #(peaks) = 0, so 82 is in the sequence. %t A296873 z = 200; b = 7; %t A296873 d[n_] := Differences[Sign[Differences[IntegerDigits[n, b]]]]; %t A296873 Select[Range [z], Count[d[#], -2] == Count[d[#], 2] &] (* A296873 *) %t A296873 Select[Range [z], Count[d[#], -2] < Count[d[#], 2] &] (* A296874 *) %t A296873 Select[Range [z], Count[d[#], -2] > Count[d[#], 2] &] (* A296875 *) %Y A296873 Cf. A296882, A296712, A296874, A296875. %K A296873 nonn,base,easy %O A296873 1,2 %A A296873 _Clark Kimberling_, Jan 09 2018