A004151 Omit trailing zeros from n.

1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 11, 12, 13, 14, 15, 16, 17, 18, 19, 2, 21, 22, 23, 24, 25, 26, 27, 28, 29, 3, 31, 32, 33, 34, 35, 36, 37, 38, 39, 4, 41, 42, 43, 44, 45, 46, 47, 48, 49, 5, 51, 52, 53, 54, 55, 56, 57, 58, 59, 6, 61, 62, 63, 64, 65, 66, 67, 68, 69, 7, 71, 72, 73, 74, 75, 76, 77, 78, 79, 8, 81, 82, 83, 84, 85, 86, 87, 88, 89, 9, 91, 92, 93, 94, 95, 96, 97, 98, 99, 1, 101, 102, 103, 104, 105, 106, 107, 108, 109, 11, 111, 112, 113, 114, 115, 116, 117, 118, 119, 12

Offset

1,2

Links

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

Formula

a(n) = a(n/10) if n mod 10 = 0, otherwise n. - Reinhard Zumkeller, Feb 02 2012

G.f. A(x) satisfies: A(x) = A(x^10) + x/(1 - x)^2 - 10*x^10/(1 - x^10)^2. - Ilya Gutkovskiy, Oct 27 2019

Sum_{k=1..n} a(k) ~ (5/11) * n^2. - Amiram Eldar, Nov 20 2022

Mathematica

Flatten[Table[n/Take[Intersection[Divisors[n], 10^Range[0, Floor[Log[10, n]]]], -1], {n, 120}]] (* Alonso del Arte, Feb 02 2012 *)
Table[n/10^IntegerExponent[n, 10], {n, 120}] (* Harvey P. Dale, May 02 2018 *)

Prog

(Haskell)
a004151 = until ((> 0) . (`mod` 10)) (`div` 10)
-- Reinhard Zumkeller, Feb 01 2012
(PARI) a(n)=n/10^valuation(n, 10) \\ Charles R Greathouse IV, Oct 31 2012
(Python)
def A004151(n):
    a, b = divmod(n, 10)
    while not b:
        n = a
        a, b = divmod(n, 10)
    return n # Chai Wah Wu, Feb 20 2024

Crossrefs

Cf. A004719, A122840.

Sequence in context: A068636 A328131 A004719 * A151765 A343750 A107603

Adjacent sequences: A004148 A004149 A004150 * A004152 A004153 A004154

Keyword

nonn,base,easy

Author

N. J. A. Sloane

Status

approved