Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #25 Apr 24 2021 21:28:34
%S 1,1,2,1,2,2,2,1,2,2,3,2,1,2,3,2,2,2,3,2,3,2,2,2,2,1,2,2,3,2,2,3,3,3,
%T 3,2,2,3,2,1,2,3,2,2,3,3,3,3,2,2,3,2,2,2,3,2,3,3,3,2,3,2,3,3,3,3,2,2,
%U 3,2,2,2,3,2,3,2,2,2,2,1,2,2,3,2,2,3,3,3,3,2
%N Number of distinct base-3 digits of n.
%C a(A031944(n)) = 3; a(A154314(n)) < 3. - _Reinhard Zumkeller_, Jan 07 2009
%C Image, under the coding sending i -> 1+floor(i/3), of the fixed point, starting with 0, of the morphism 0 -> 012, 1 -> 314, 2 -> 542, 3 -> 336, 4 -> 644, 5 -> 565, 6 -> 666. - _Jeffrey Shallit_, May 15 2016
%H Antti Karttunen, <a href="/A043530/b043530.txt">Table of n, a(n) for n = 1..19683</a>
%t Table[Length[Union[IntegerDigits[n,3]]],{n,90}] (* _Harvey P. Dale_, May 13 2020 *)
%o (PARI) a(n) = #vecsort(digits(n,3),,8); \\ _Michel Marcus_, May 16 2016
%Y Cf. A007089, A031944, A037897, A154314.
%K nonn,base
%O 1,3
%A _Clark Kimberling_