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A321800 Delete the decimal digits of n that appear exactly once; write -1 if all digits disappear. 4

%I #13 Nov 20 2018 22:55:33

%S -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,11,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,22,

%T -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,33,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,44,-1,

%U -1,-1,-1,-1,-1,-1,-1,-1,-1,55,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,66,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,77,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,88,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,99,0,11,-1,-1,-1,-1,-1,-1,-1,-1,11,111,11,11,11,11,11,11,11,11,-1,11,22,-1,-1,-1,-1,-1,-1,-1,-1,11,-1,33,-1,-1,-1,-1,-1,-1,-1,11,-1,-1,44,-1,-1,-1,-1,-1,-1,11,-1,-1,-1,55,-1,-1,-1,-1,-1,11,-1,-1,-1,-1,66,-1,-1,-1,-1,11,-1,-1,-1,-1,-1,77,-1,-1,-1,11,-1,-1,-1,-1,-1,-1,88,-1,-1,11,-1,-1,-1,-1,-1,-1,-1,99

%N Delete the decimal digits of n that appear exactly once; write -1 if all digits disappear.

%C A companion sequence to A320485.

%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 -1 for the result (A321797 is another version, which uses 0 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="/A321800/b321800.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 -1.

%o (Python)

%o def A321800(n):

%o return (lambda x: int(x) if x != '' else -1)(''.join(d if str(n).count(d) != 1 else '' for d in str(n)))

%Y Cf. A320485, A321797.

%K sign,base,look

%O 0,12

%A _Chai Wah Wu_, Nov 19 2018

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Last modified March 29 03:51 EDT 2024. Contains 371264 sequences. (Running on oeis4.)