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A032865 Numbers whose base-10 representation Sum_{i=0..m} d(i)*10^i has d(m) > d(m-1) < d(m-2) > ... 10
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, 61, 62, 63, 64, 65, 70, 71, 72, 73, 74, 75, 76, 80, 81, 82, 83, 84, 85, 86, 87, 90, 91, 92, 93, 94, 95, 96, 97, 98, 101, 102, 103, 104, 105, 106, 107 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Every other digit must be strictly less than its neighbor(s). - M. F. Hasler, Oct 05 2018

LINKS

M. F. Hasler, Table of n, a(n) for n = 1..10000

MATHEMATICA

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 *)

PROG

(PARI) is(n)=!for(i=2, #n=digits(n), (n[i-1]-n[i])*(-1)^i>0||return) \\ M. F. Hasler, Oct 05 2018

CROSSREFS

Cf. A032858 .. A032864 for base-3 .. 9 variants.

Sequence in context: A247808 A247807 A247804 * A032889 A308393 A009995

Adjacent sequences:  A032862 A032863 A032864 * A032866 A032867 A032868

KEYWORD

nonn,base

AUTHOR

Clark Kimberling

EXTENSIONS

Name corrected and cross-references and a(1) = 0 prepended by M. F. Hasler, Oct 05 2018

STATUS

approved

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Last modified October 21 20:44 EDT 2019. Contains 328315 sequences. (Running on oeis4.)