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a(n) = smallest number which has in its Spanish name the letter "s" in the n-th position,or -1 if no such number exists.
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%I #2 Mar 31 2012 14:00:43

%S 6,-1,2,3,-1,16,26,3006,16,23,32,33,43,53,116,123,132,133,143,153,232,

%T 233,243,253,353,443,453,1353,1443,1453,2353,2443,2453,3453,4443,4453

%N a(n) = smallest number which has in its Spanish name the letter "s" in the n-th position,or -1 if no such number exists.

%C a(1)=Seis, a(3)=doS, a(4)= treS

%K word,sign

%O 1,1

%A _Claudio Meller_, Aug 26 2009