A180412 Lexicographically earliest increasing sequence of numbers with all odd digits alternating with numbers with all even digits.

1, 2, 3, 4, 5, 6, 7, 8, 9, 20, 31, 40, 51, 60, 71, 80, 91, 200, 311, 400, 511, 600, 711, 800, 911, 2000, 3111, 4000, 5111, 6000, 7111, 8000, 9111, 20000, 31111, 40000, 51111, 60000, 71111, 80000, 91111, 200000, 311111, 400000, 511111, 600000, 711111, 800000, 911111, 2000000

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

11 is all odd digits. The next number in which all of the digits are even is 20. The next number in which all of the digits are odd is 31.

Mathematica

nxt[n_]:=Module[{fidn=First[IntegerDigits[n]], len=IntegerLength[n]}, Which[fidn==9, 2*10^len, EvenQ[ fidn], FromDigits[PadRight[{fidn+1}, len, 1]], OddQ[fidn], FromDigits[PadRight[ {fidn+ 1}, len, 0]]]]; NestList[nxt, 1, 50] (* Harvey P. Dale, Nov 26 2013 *)

Crossrefs

Cf. A014261, A014263.

Sequence in context: A098779 A276822 A326106 * A290951 A114800 A079170

Adjacent sequences: A180409 A180410 A180411 * A180413 A180414 A180415

Keyword

easy,nonn,base

Author

Dominick Cancilla, Sep 02 2010

Extensions

Name edited by Michel Marcus, Apr 16 2023

Status

approved