A050715 Inserting a digit '5' between adjacent digits of n makes a prime.

11, 17, 21, 27, 33, 39, 47, 57, 63, 69, 71, 77, 83, 87, 89, 93, 103, 129, 139, 141, 151, 159, 189, 199, 207, 213, 223, 237, 243, 247, 267, 279, 291, 301, 303, 309, 313, 319, 321, 327, 333, 373, 379, 381, 391, 403, 429, 453, 457, 469, 471, 477, 483, 493, 499

Offset

1,1

Links

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

Example

373 becomes 3(5)7(5)3 which is prime 35753.

Mathematica

Select[Range[10, 500], PrimeQ[FromDigits[Riffle[IntegerDigits[#], 5]]]&] (* Harvey P. Dale, Apr 07 2018 *)

Crossrefs

Cf. A050674, A050711, A050712, A050713, A050714, A050716, A050717, A050718, A050719.

Sequence in context: A322476 A176603 A325902 * A006618 A184551 A190039

Adjacent sequences: A050712 A050713 A050714 * A050716 A050717 A050718

Keyword

nonn,base

Author

Patrick De Geest, Aug 15 1999

Extensions

Offset changed to 1 by Georg Fischer, Oct 15 2019

Status

approved