A145711 Number of primes p in the range 9 < p <= prime(10^n) that have most significant and least significant decimal digit both equal to 7.

0, 0, 32, 264, 2103, 17891, 155956, 1379175, 12374435, 112213301

Offset: 1

Author

Enoch Haga, Oct 16 2008

Keywords

• base
• hard
• nonn

Examples

			a(3) = 32 because there are 32 primes in the set, from p(129)=727 to p(962)=7577.
		

Crossrefs

Cf. A145709 - A145713.

Extensions

Edited by N. J. A. Sloane, Aug 16 2010, based on emails from Charles R Greathouse IV, Alois P. Heinz, R. J. Mathar and Jack Brennen (who computed a(6)).

Offset changed to agree with A145713 by D. S. McNeil, Aug 29 2010

a(9), a(10) from D. S. McNeil, Aug 29 2010