A050714 Inserting a digit '4' between adjacent digits of n makes a prime.

19, 21, 37, 39, 43, 49, 51, 57, 61, 63, 67, 73, 91, 97, 113, 119, 123, 129, 131, 137, 147, 149, 153, 159, 171, 177, 183, 197, 203, 209, 227, 243, 257, 279, 281, 287, 293, 311, 317, 353, 359, 369, 377, 381, 383, 387, 389, 399, 401, 429, 449, 453, 459, 461, 467

Offset: 1

Author

Patrick De Geest, Aug 15 1999

Keywords

• nonn
• base

Examples

			389 becomes 3(4)8(4)9 which is prime 34849.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A050674, A050711, A050712, A050713, A050715, A050716, A050717, A050718, A050719.

Programs

Mathematica

Select[Range[10,500],PrimeQ[FromDigits[Riffle[IntegerDigits[#],4]]]&] (* Harvey P. Dale, Nov 03 2024 *)