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%I #6 Jun 07 2013 17:39:43
%S 123,1234,1234567,12345678901,12345678901234567,
%T 123456789012345678901234567,1234567890123456789012345678901
%N Semiprimes with consecutive digits starting with 1.
%e 123=3*41, 1234=2*617, 1234567=127*9721, 12345678901=857*14405693,..
%t f1[n_]:=Last@RealDigits[n,10][[1]]; f2[n_]:=Last/@FactorInteger[n]=={1,1}; lst={};lst2={};Do[AppendTo[lst,f1[n]];a=FromDigits[lst];If[f2[a],(*Print[a];*)AppendTo[lst2,a]],{n,43}];lst2
%t Select[Table[FromDigits[PadRight[{},n,Join[Range[9],{0}]]],{n,40}], PrimeOmega[ #]==2&] (* _Harvey P. Dale_, Jun 07 2013 *)
%K nonn,base
%O 1,1
%A _Vladimir Joseph Stephan Orlovsky_, Mar 11 2010
%E Next terms have 124, 157, 247, ... decimal digits.
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