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A050713
Inserting a digit '3' between adjacent digits of n makes a prime.
9
11, 17, 19, 23, 29, 31, 37, 41, 43, 49, 61, 73, 79, 89, 97, 103, 107, 131, 137, 139, 157, 163, 181, 191, 193, 209, 211, 233, 239, 241, 251, 257, 259, 263, 281, 283, 307, 331, 353, 367, 379, 391, 397, 407, 413, 427, 431, 463, 493, 521, 523, 529, 547, 563, 569
OFFSET
1,1
LINKS
EXAMPLE
407 becomes 4(3)0(3)7 which is prime 43037.
MATHEMATICA
Select[Range[10, 600], PrimeQ[FromDigits[Riffle[IntegerDigits[#], 3]]]&] (* Harvey P. Dale, Dec 23 2023 *)
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Aug 15 1999
STATUS
approved