A001633 Numbers with an odd number of digits.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145

Offset

1,3

Comments

The lower and upper asymptotic densities of this sequence are 1/11 and 10/11, respectively. - Amiram Eldar, Feb 01 2021

Links

T. D. Noe, Table of n, a(n) for n = 1..1000

Formula

A055642(a(n)) mod 2 = 1. - Reinhard Zumkeller, Jul 14 2014

Except for k = 0, if k is in this sequence, floor(log_10 k) is even; e.g., if k has three digits, 2 <= log_10 k < 3. - Alonso del Arte, Feb 03 2020

Mathematica

Select[Range[0, 145], OddQ[Length[IntegerDigits[#]]] &] (* T. D. Noe, Aug 09 2012 *)
Table[Range[10^n, 10^(n+1)-1], {n, 0, 4, 2}]//Flatten (* Harvey P. Dale, Nov 29 2022 *)

Prog

(Haskell)
a001633 n = a001633_list !! (n-1)
a001633_list = filter (odd . a055642) [0..]
-- Reinhard Zumkeller, Jul 14 2014
(PARI) is(n)=#Str(n)%2 \\ Charles R Greathouse IV, Nov 26 2018
(Scala) (0 to 199).filter(Integer.toString(_).length % 2 == 1) // Alonso del Arte, Feb 03 2020

Crossrefs

Cf. A001637 (complement), A055642.

Sequence in context: A239138 A345964 A298425 * A171120 A092907 A051022

Adjacent sequences: A001630 A001631 A001632 * A001634 A001635 A001636

Keyword

nonn,base,easy

Author

N. J. A. Sloane

Status

approved