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%I #11 Nov 03 2018 17:49:10
%S 0,1,3,4,5,6,7,8,9,10,12,15,17,19,21,24,25,26,27,28,29,30,31,33,34,35,
%T 36,37,38,39,40,41,43,44,45,46,47,48,49,50,51,53,54,55,56,57,58,59,60,
%U 61,63,64,65,66,67,68,69,70,71,73,74,75,76,77,78,79,80,81,83,84,85,86,87,88,89,90,91,93,94,95,96,97,98,99,100,102,105,107
%N a(0)=0; thereafter add the smallest positive number that is not a substring.
%F a(n) = A261793(n) for n >= 1. - _Georg Fischer_, Oct 30 2018
%e In a(13) = 19 we can see a 1 but no 2, so a(14) = 19+2 = 21. Now we can see a 1 and a 2 but no 3, so a(15) = 21+3 = 24.
%t r[n_]:=Rest[Subsets[IntegerDigits[n]]];
%t s[n_]:=Union[FromDigits/@r[n]];firstN[0]=1;firstN[1]=2;
%t firstN[n_]:=Min[Select[Range[Last[s[n]]],FreeQ[s[n],#]&]];
%t nextTerm[n_]:=n+firstN[n];FoldList[nextTerm[#]&,0,Range@87] (* _Ivan N. Ianakiev_, Sep 20 2015 *)
%Y Decimal analog of A260273.
%Y Cf. A261793.
%K nonn,base
%O 0,3
%A _N. J. A. Sloane_, Sep 19 2015
%E Typo in a(61) corrected by _Ivan N. Ianakiev_, Sep 20 2015