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A050712
Inserting a digit '2' between adjacent digits of n makes a prime.
10
17, 23, 27, 29, 41, 51, 53, 77, 81, 83, 87, 89, 99, 127, 133, 139, 141, 157, 171, 181, 183, 189, 193, 207, 213, 219, 229, 261, 271, 277, 291, 307, 309, 331, 333, 337, 343, 349, 361, 403, 421, 423, 427, 433, 477, 481, 489, 493, 499, 501, 507, 511, 517, 523
OFFSET
1,1
LINKS
EXAMPLE
333 becomes 3(2)3(2)3 which is prime 32323.
MATHEMATICA
Select[Range[10, 600], PrimeQ[FromDigits[Riffle[IntegerDigits[#], 2]]]&] (* Harvey P. Dale, Sep 13 2014 *)
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Aug 15 1999
EXTENSIONS
Offset changed to 1 by Georg Fischer, Oct 15 2019
STATUS
approved