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

1,1

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

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 *)

Prog

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

Crossrefs

Cf. A044821, A171903, A171904.

Sequence in context: A109303 A338214 A068520 * A033283 A044851 A276769

Adjacent sequences: A171898 A171899 A171900 * A171902 A171903 A171904

Keyword

base,nonn

Author

Reinhard Zumkeller, Feb 07 2010

Status

approved