A321801 Delete all consecutive identical decimal digits of n; write 0 if all digits disappear.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 0, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 0, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 0, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 0, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 0, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 0, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 0, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 0, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 0, 1, 101, 102, 103, 104, 105, 106, 107, 108, 109, 0, 0, 2, 3, 4, 5, 6, 7, 8, 9, 120, 121, 1, 123, 124, 125, 126, 127, 128, 129, 130, 131

Offset

0,3

Comments

Consecutive identical digits of n are erased. Leading zeros are erased unless the result is 0. If all digits are erased, we write 0 for the result (A321802 is another version, which uses -1 for the empty string).

More than the usual number of terms are shown in order to reach some interesting examples. Agrees with A320486 for n < 101.

Links

Paolo Xausa, Table of n, a(n) for n = 0..10000

Example

12311 becomes 123, 1123 becomes 23, 11231 becomes 231, and 110232 becomes 232 (as we don't accept leading zeros). Note that 112233 disappears immediately and we get 0.
1110, 11000, 1100011 all become 0.

Mathematica

A321801[n_]:=FromDigits[Flatten[Select[Split[IntegerDigits[n]], Length[#]==1&]]]; Array[A321801, 100, 0] (* Paolo Xausa, Nov 14 2023 *)

Prog

(Python)
from re import split
def A321801(n):
    return int('0'+''.join(d if len(d) == 1 else '' for d in split('(0+)|(1+)|(2+)|(3+)|(4+)|(5+)|(6+)|(7+)|(8+)|(9+)', str(n)) if d != '' and d != None))
(PARI) A321801(n)={forstep(i=#n=digits(n), 2, -1, n[i]!=n[i-1]&&next; if(i<3||n[i-2]!=n[i], n=n[^i]; i--); n=n[^i]); fromdigits(n)} \\ M. F. Hasler, Nov 20 2018

Crossrefs

Cf. A320486, A321802.

Sequence in context: A329079 A306580 A320486 * A278946 A322629 A190599

Adjacent sequences: A321798 A321799 A321800 * A321802 A321803 A321804

Keyword

nonn,base

Author

Chai Wah Wu, Nov 19 2018

Status

approved