%N Delete the decimal digits of n that appear exactly once; write 0 if all digits disappear.
%C A companion sequence to A320486.
%C Digits that appear exactly once in n are erased. Leading zeros are erased unless the result is 0. If all digits are erased, we write 0 for the result (A321800 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.
%H Chai Wah Wu, <a href="/A321797/b321797.txt">Table of n, a(n) for n = 0..10000</a>
%e 12321 becomes 1221, 1123 becomes 11, 11231 becomes 111, and 100223 becomes 22 (as we don't accept leading zeros). Note that 12345 disappears immediately and we get 0.
%o def A321797(n):
%o return int('0'+''.join(d if str(n).count(d) != 1 else '' for d in str(n)))
%Y Cf. A320486, A321800.
%A _Chai Wah Wu_, Nov 19 2018