A125197 Numbers such that pre- and post-concatenating 7, 13 and 31 results in six primes.

19, 3583, 11287, 62989, 63409, 89491, 93187, 104107, 106783, 155851, 178351, 1082467, 1219399, 1510207, 1566613, 1581469, 2246173, 2920693, 3081499, 3342277, 3523339, 3781849, 3820543, 4010161, 4824163, 4865827, 6091597

Offset

1,1

Comments

It is conjectured that 7, 13 and 31 is the only triple with this property

Links

Table of n, a(n) for n=1..27.

Example

3583 is a member as 3583, 73583, 35837, 123583, 358313, 313583, 358331 are all prime.

Crossrefs

Sequence in context: A287938 A225602 A195756 * A375090 A238563 A281820

Adjacent sequences: A125194 A125195 A125196 * A125198 A125199 A125200

Keyword

hard,nonn,base

Author

Anton Vrba (antonvrba(AT)yahoo.com), Jan 13 2007

Status

approved