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A036976
Becomes a prime if a 1 is inserted before each digit.
1
1, 3, 7, 9, 17, 23, 27, 39, 51, 63, 69, 81, 93, 119, 121, 127, 137, 161, 193, 199, 203, 209, 233, 271, 301, 311, 313, 323, 331, 337, 343, 359, 361, 367, 371, 373, 431, 439, 443, 451, 463, 469, 479, 481, 497, 503, 523, 557, 577, 583, 587, 607, 641, 661, 677
OFFSET
0,2
EXAMPLE
E.g. 27 -> 1217 is prime.
MATHEMATICA
Select[Range[700], PrimeQ[FromDigits[Join[{1}, Riffle[ IntegerDigits[ #], 1]]]]&] (* Harvey P. Dale, Jul 24 2012 *)
CROSSREFS
Cf. A036977.
Sequence in context: A064194 A036978 A079464 * A230116 A361005 A031273
KEYWORD
nonn,base,easy
AUTHOR
EXTENSIONS
More terms from Erich Friedman.
STATUS
approved