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 A321801 Delete all consecutive identical decimal digits of n; write 0 if all digits disappear. 6

%I

%S 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,

%T 27,28,29,30,31,32,0,34,35,36,37,38,39,40,41,42,43,0,45,46,47,48,49,

%U 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

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

%C 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).

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

%e 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.

%e 1110, 11000, 1100011 all become 0.

%o (Python)

%o from re import split

%o def A321801(n):

%o 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))

%o (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

%Y Cf. A320486, A321802.

%K nonn,base

%O 0,3

%A _Chai Wah Wu_, Nov 19 2018

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Last modified September 28 17:43 EDT 2020. Contains 337393 sequences. (Running on oeis4.)