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
KEYWORD
nonn,base,easy
AUTHOR
STATUS
approved