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%I #7 Jul 29 2012 11:36:19
%S 1,3,7,9,17,23,27,39,51,63,69,81,93,119,121,127,137,161,193,199,203,
%T 209,233,271,301,311,313,323,331,337,343,359,361,367,371,373,431,439,
%U 443,451,463,469,479,481,497,503,523,557,577,583,587,607,641,661,677
%N Becomes a prime if a 1 is inserted before each digit.
%e E.g. 27 -> 1217 is prime.
%t Select[Range[700],PrimeQ[FromDigits[Join[{1},Riffle[ IntegerDigits[ #],1]]]]&] (* _Harvey P. Dale_, Jul 24 2012 *)
%Y Cf. A036977.
%K nonn,base,easy
%O 0,2
%A _N. J. A. Sloane_.
%E More terms from _Erich Friedman_.
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