A102501 Primes of the concatenated form 7nn7.

715157, 718187, 719197, 734347, 736367, 739397, 748487, 752527, 757577, 760607, 767677, 775757, 779797, 781817, 785857, 796967, 797977, 7100510057, 7102010207, 7103010307, 7104710477, 7105410547, 7106210627, 7106510657, 7107410747

Offset

1,1

Links

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

Example

715157 is prime and of the form 7nn7 for n=15.
7100510057 is prime and of the form 7nn7 for n=1005.

Mathematica

Select[Table[FromDigits[Join[{7}, IntegerDigits[n], IntegerDigits[n], {7}]], {n, 1100}], PrimeQ] (* Harvey P. Dale, Jun 05 2024 *)

Crossrefs

Cf. A102897 for sequence of all numbers of form 7nn7. A102500 for the n values corresponding to the primes in this sequence.

Sequence in context: A234757 A232578 A249210 * A301643 A252887 A204403

Adjacent sequences: A102498 A102499 A102500 * A102502 A102503 A102504

Keyword

easy,nonn,base

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 13 2005

Status

approved