|
%I #18 Oct 06 2018 11:47:43
%S 0,1,2,3,4,5,6,7,8,9,10,20,21,30,31,32,40,41,42,43,50,51,52,53,54,60,
%T 61,62,63,64,65,70,71,72,73,74,75,76,80,81,82,83,84,85,86,87,90,91,92,
%U 93,94,95,96,97,98,101,102,103,104,105,106,107
%N Numbers whose base-10 representation Sum_{i=0..m} d(i)*10^i has d(m) > d(m-1) < d(m-2) > ...
%C Every other digit must be strictly less than its neighbor(s). - _M. F. Hasler_, Oct 05 2018
%H M. F. Hasler, <a href="/A032865/b032865.txt">Table of n, a(n) for n = 1..10000</a>
%t sdQ[n_]:=Module[{s=Sign[Differences[IntegerDigits[n, 10]]]}, s==PadRight[{}, Length[s], {-1, 1}]]; Select[Range[0, 700], sdQ] (* _Vincenzo Librandi_, Oct 06 2018 *)
%o (PARI) is(n)=!for(i=2,#n=digits(n),(n[i-1]-n[i])*(-1)^i>0||return) \\ _M. F. Hasler_, Oct 05 2018
%Y Cf. A032858 .. A032864 for base-3 .. 9 variants.
%K nonn,base
%O 1,3
%A _Clark Kimberling_
%E Name corrected and cross-references and a(1) = 0 prepended by _M. F. Hasler_, Oct 05 2018
|
