A004216 a(n) = floor(log_10(n)).

0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

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

Crossrefs

Cf. A055642.

Programs

Haskell

a004216 n = if n <= 9 then 0 else 1 + a004216 (n `div` 10)
-- Reinhard Zumkeller, Dec 22 2012

Mathematica

Table[ Length[ IntegerDigits[n, 10] ] - 1, {n, 105}] (* Jean-François Alcover, Jun 10 2013 *)
Table[Floor[Log10[n]], {n, 105}] (* L. Edson Jeffery, Jul 09 2014 *)

PARI

a(n) = logint(n, 10); \\ Michel Marcus, Oct 16 2021

Python

def A004216(n): return len(str(n))-1 # Chai Wah Wu, May 02 2023

Formula

a(n) = if n > 9 then a(floor(n/10)) + 1, else 0. - Reinhard Zumkeller, Oct 31 2001

a(n) = A055642(n) - 1. - L. Edson Jeffery, Jul 09 2014

G.f.: (1/(1 - x))*Sum_{k>=1} x^(10^k). - Ilya Gutkovskiy, Jan 08 2017

Extensions

More terms from James Sellers, Sep 19 2000