A050718 Inserting a digit '8' between adjacent decimal digits of n makes a prime.

11, 21, 23, 33, 39, 47, 57, 63, 77, 81, 83, 87, 93, 109, 111, 127, 129, 141, 153, 157, 177, 201, 207, 211, 213, 223, 229, 237, 267, 279, 303, 313, 319, 321, 327, 373, 417, 421, 433, 441, 447, 459, 471, 477, 483, 489, 499, 519, 541, 567, 577, 579, 589, 607

Offset

1,1

Comments

Arguably 2, 3, 5, and 7 should be in this sequence. - Charles R Greathouse IV, Sep 25 2012

Links

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

Example

177 becomes 1(8)7(8)7 which is the prime 18787.

Mathematica

Select[Range[10, 700], PrimeQ[FromDigits[Riffle[IntegerDigits[#], 8]]]&] (* Harvey P. Dale, Sep 18 2013 *)

Crossrefs

Cf. A050674, A050711-A050719.

Sequence in context: A117841 A105956 A178413 * A360372 A350766 A189226

Adjacent sequences: A050715 A050716 A050717 * A050719 A050720 A050721

Keyword

nonn,base

Author

Patrick De Geest, Aug 15 1999

Status

approved