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 A004216 a(n) = floor(log_10(n)). 25
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,100 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 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 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 *) PROG (Haskell) a004216 n = if n <= 9 then 0 else 1 + a004216 (n `div` 10) -- Reinhard Zumkeller, Dec 22 2012 (PARI) a(n) = logint(n, 10); \\ Michel Marcus, Oct 16 2021 CROSSREFS Cf. A055642. Sequence in context: A329030 A027388 A114295 * A076489 A211666 A297037 Adjacent sequences: A004213 A004214 A004215 * A004217 A004218 A004219 KEYWORD nonn AUTHOR EXTENSIONS More terms from James A. Sellers, Sep 19 2000 STATUS approved

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Last modified December 7 22:27 EST 2022. Contains 358671 sequences. (Running on oeis4.)