A068677 Numbers that yield a prime when a 7 is prefixed or suffixed to them.

1, 3, 9, 19, 27, 33, 39, 57, 61, 87, 97, 109, 121, 127, 129, 159, 177, 187, 213, 229, 237, 243, 247, 283, 321, 351, 369, 417, 433, 451, 459, 481, 487, 507, 523, 529, 541, 547, 573, 589, 603, 621, 639, 673, 691, 699, 717, 723, 741, 753, 757, 793, 823, 829, 853

Offset

1,2

Links

Table of n, a(n) for n=1..55.

Example

129 belongs to this sequence as both 1297 and 7129 are primes.

Crossrefs

Cf. A068673, A068674.

Sequence in context: A056259 A056682 A032670 * A069832 A057257 A029464

Adjacent sequences: A068674 A068675 A068676 * A068678 A068679 A068680

Keyword

base,easy,nonn

Author

Amarnath Murthy, Mar 02 2002

Extensions

More terms from Sascha Kurz, Mar 17 2002

Status

approved