A050712 - OEIS

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A050712

Inserting a digit '2' between adjacent digits of n makes a prime.

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1001

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 *)

CROSSREFS

Cf. A050674, A050711, A050713, A050714, A050715, A050716, A050717, A050718, A050719.

Sequence in context: A346163 A370853 A214791 * A068581 A166864 A137670