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%I #12 Jan 22 2020 02:54:25
%S 9,19,1,10,0,20,2,12,11,13,3,23,21,14,4,24,22,25,5,15,16,6,26,27,7,17,
%T 18,8,28,29,32,30,31,33,34,35,36,37,38,39,43,40,41,42,44,45,46,47,48,
%U 49,54,50,51,52,53,55,56,57,58,59,65,60,61,62,63,64,66,67,68,69,76,70
%N a(1)=9, a(n) = smallest integer not previously used which contains a digit from a(n-1).
%H Robert Israel, <a href="/A107780/b107780.txt">Table of n, a(n) for n = 1..10000</a>
%p S:= [$0..100]:
%p Res:= 9: S:= subs(9=NULL,S):
%p digs:= {9}:
%p while S <> [] do
%p found:= false;
%p for i from 1 to nops(S) while not found do
%p ndigs:= convert(convert(S[i],base,10),set);
%p if ndigs intersect digs <> {} then
%p found:= true;
%p Res:=Res, S[i];
%p S:= subsop(i=NULL, S);
%p digs:= ndigs;
%p fi
%p od;
%p if not found then break fi;
%p od:
%p Res; # _Robert Israel_, Jan 22 2020
%t f[l_] := Block[{c = 0}, While[ MemberQ[l, c] || Intersection @@ IntegerDigits /@{Last[l], c}=={}, c++ ];Return[Append[l, c]]];Nest[f, {9}, 70] (* _Ray Chandler_, Jul 19 2005 *)
%Y Cf. A107353 a(1)=0, A107772 a(1)=1, A107773 a(1)=2, A107774 a(1)=3, A107775 a(1)=4, A107776 a(1)=5, A107777 a(1)=6, A107778 a(1)=7, A107779 a(1)=8, A107781 a(1)=10.
%K base,nonn
%O 1,1
%A _Eric Angelini_ & _Zak Seidov_, May 24 2005
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