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

Author

Dominick Cancilla, Sep 02 2010

Keywords

• easy
• nonn
• base

Examples

			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.
		

Links

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

Crossrefs

Cf. A014261, A014263.

Programs

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 *)

Extensions

Name edited by Michel Marcus, Apr 16 2023