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A009994 Numbers with digits in nondecreasing order. 28
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 22, 23, 24, 25, 26, 27, 28, 29, 33, 34, 35, 36, 37, 38, 39, 44, 45, 46, 47, 48, 49, 55, 56, 57, 58, 59, 66, 67, 68, 69, 77, 78, 79, 88, 89, 99, 111, 112, 113, 114, 115, 116, 117, 118, 119, 122 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Record values and occurrences of A004185. - Reinhard Zumkeller, Dec 05 2009

A193581(a(n)) = 0. - Reinhard Zumkeller, Aug 10 2011

REFERENCES

Amarnath Murthy and Robert J. Clarke, Some Properties of Staircase sequence, Mathematics & Informatics Quarterly, Volume 11, No. 4, November 2001.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

D. Applegate, M. LeBrun, N. J. A. Sloane, Dismal Arithmetic, J. Int. Seq. 14 (2011) # 11.9.8.

Eric Weisstein's World of Mathematics, Digit.

Index entries for 10-automatic sequences.

FORMULA

a(n) >> exp(n^(1/10)). - Charles R Greathouse IV, Mar 15 2014

MATHEMATICA

Select[Range[0, 125], LessEqual@@IntegerDigits[#]&] (* Ray Chandler, Oct 25 2011 *)

PROG

(Haskell)

import Data.Set (fromList, deleteFindMin, insert)

a009994 n = a009994_list !! n

a009994_list = 0 : f (fromList [1..9]) where

   f s = m : f (foldl (flip insert) s' $ map (10*m +) [m `mod` 10 ..9])

         where (m, s') = deleteFindMin s

-- Reinhard Zumkeller, Aug 10 2011

(PARI) is(n)=n=digits(n); n==vecsort(n) \\ Charles R Greathouse IV, Dec 03 2013

(Python)

from itertools import combinations_with_replacement

def A009994generator():

    yield 0

    l = 1

    while True:

        for i in combinations_with_replacement('123456789', l):

            yield int(''.join(i))

        l += 1 # Chai Wah Wu, Nov 11 2015

CROSSREFS

Apart from the first term, a subsequence of A052382. A254143 is a subsequence.

Cf. A152054, A036839.

Sequence in context: A131058 A032857 A072544 * A239016 A102827 A190221

Adjacent sequences:  A009991 A009992 A009993 * A009995 A009996 A009997

KEYWORD

nonn,base,look,changed

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified September 20 10:29 EDT 2017. Contains 292265 sequences.