A004720 Delete all digits '1' from the sequence of nonnegative integers.

0, 2, 3, 4, 5, 6, 7, 8, 9, 0, 2, 3, 4, 5, 6, 7, 8, 9, 20, 2, 22, 23, 24, 25, 26, 27, 28, 29, 30, 3, 32, 33, 34, 35, 36, 37, 38, 39, 40, 4, 42, 43, 44, 45, 46, 47, 48, 49, 50, 5, 52, 53, 54, 55, 56, 57, 58, 59, 60, 6, 62, 63, 64, 65, 66, 67, 68, 69, 70, 7, 72, 73, 74, 75

Offset

1,2

Comments

Similar to A004176. - R. J. Mathar, Oct 28 2008

More precisely, in A004176 the term becomes 0 if no digit remains, e.g., for 1 or 11, whereas here in such a case the integer is completely skipped (as in A004719, A004721, ... which are the analogs for deleting 0, 2, ...). - M. F. Hasler, Feb 01 2016

Links

Sean A. Irvine, Table of n, a(n) for n = 1..1000

Example

The first nonnegative integer, 0, remains as a(1).
The second nonnegative integer, 1, completely disappears upon removal of the digit 1.
The third nonnegative integer, 2, remains as a(2).
The number 10 becomes a(10)=0.
The number 11 completely disappears upon removal of both its digits '1'.
The number 12 becomes a(11)=2.

Maple

f:= proc(n) local L, i;
     L:= subs(1=NULL, convert(n, base, 10));
     if L = [] then NULL
     else add(L[i]*10^(i-1), i=1..nops(L))
     fi
end proc:
map(f, [$0..100]); # Robert Israel, Feb 07 2016

Mathematica

f[n_] := Block[{a = DeleteCases[ IntegerDigits[n], 1]}, If[a != {}, FromDigits@ a, b]]; DeleteCases[ Array[f, 75, 0], b] (* Robert G. Wilson v, Feb 05 2016 *)

Prog

(PARI) for(n=0, 99, if(t=select(d->d!="1", Vec(Str(n))), print1(concat(t)", "))) \\ M. F. Hasler, Feb 01 2016
(Python)
def A004720(n):
    l = len(str(n-1))
    m = (10**l-1)//9
    k = n + l - 2 + int(n+l-1 >= m)
    return 0 if k == m else int(str(k).replace('1', '')) # Chai Wah Wu, Apr 20 2021

Crossrefs

See A004176 for another version.

Cf. A004719, A004721, ...

Sequence in context: A309590 A169931 A141022 * A088118 A330633 A257850

Adjacent sequences: A004717 A004718 A004719 * A004721 A004722 A004723

Keyword

base,nonn,nice,look

Author

N. J. A. Sloane

Extensions

Corrected by T. D. Noe, Sep 19 2008

Entry revised by N. J. A. Sloane and M. F. Hasler following a suggestion from Sean A. Irvine, Feb 01 2016

Status

approved