A337864 a(n) is the number formed by removing from n each digit if it is a duplicate of the previous digit, from left to right.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 2, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 3, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 4, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 5, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 6, 67, 68, 69, 70, 71, 72, 73, 74

Offset

0,3

Comments

Please see discussion in A337857.

Similar to A137564 from which first differs at a(101) = 101 here, there a(101) = 10.

Differs from A106612 starting at n=100. - R. J. Mathar, Oct 08 2020

Links

Michael S. Branicky, Table of n, a(n) for n = 0..10000

Example

a(100) = 10. Note that the second zero from the index n = 100 has been removed.
a(101) = 101.
a(1211323171) = 121323171. Note that the third "1" from the index n has been removed).

Prog

(Perl) sub a {my($n)=@_; $n =~ s/(.)\1+/$1/g; $n} # Kevin Ryde, Oct 04 2020
(Python)
from itertools import groupby
def a(n): return int("".join(k for k, g in groupby(str(n))))
print([a(n) for n in range(75)]) # Michael S. Branicky, Jul 23 2022
(PARI) a(n) = if(n < 10, return(n)); if(n%10 == (n\10)%10, return(a(n\10)), return(a(n\10)*10+n%10)) \\ David A. Corneth, Jul 23 2022

Crossrefs

Cf. A043096 (fixed points a(n)=n).

Cf. A137564, A337857.

Cf. A090079 (in binary).

Sequence in context: A180409 A320485 A321802 * A106612 A137564 A056960

Adjacent sequences: A337861 A337862 A337863 * A337865 A337866 A337867

Keyword

base,nonn

Author

Rodolfo Kurchan, Sep 27 2020

Status

approved