A171901 Numbers with at least two identical neighboring digits in their decimal representation.

11, 22, 33, 44, 55, 66, 77, 88, 99, 100, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 122, 133, 144, 155, 166, 177, 188, 199, 200, 211, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 233, 244, 255, 266, 277, 288, 299, 300, 311, 322, 330, 331, 332, 333

Offset: 1

Author

Reinhard Zumkeller, Feb 07 2010

Keywords

• base
• nonn

Comments

A171902(n) = a(n+1) - a(n) <= 11.

Complement of A043096; A196368(a(n)) = 0.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A044821, A171903, A171904.

Programs

Haskell

import Data.List (elemIndices)
a171901 n = a171901_list !! n
a171901_list = elemIndices 0 a196368_list
-- Reinhard Zumkeller, Oct 29 2001

Mathematica

Select[Range[350],SequenceCount[IntegerDigits[#],{_,x_,x_,_}]>0&] (* The program uses the SequenceCount function from Mathematica version 10 *) (* Harvey P. Dale, May 14 2016 *)

Python

def is_ok(n):
    s = str(n)
    return any(s[i] == s[i - 1] for i in range(1, len(s)))
A171901_list = [n for n in range(400) if is_ok(n)] # Chai Wah Wu, Feb 14 2019