A108794 Primes whose 10's complement is a semiprime, i.e., p is prime and 10^L - p is a semiprime, where L is the number of digits in p.

13, 23, 31, 43, 61, 67, 79, 101, 107, 131, 149, 151, 157, 193, 197, 211, 229, 233, 251, 263, 269, 277, 283, 293, 311, 313, 331, 367, 389, 409, 419, 421, 449, 457, 463, 467, 499, 503, 547, 563, 587, 593, 607, 619, 659, 661, 673, 677, 691, 701, 709, 733, 751

Offset

1,1

Comments

Some twin prime terms are (149,151), (311,313), (419,421), (659,661), ... Conjecture: there are infinitely many twin primes in this sequence.

Links

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

Example

563 is a term because it is prime and 10^3 - 563 = 437 = 19*23.

Mathematica

Select[Prime[Range[200]], PrimeOmega[10^IntegerLength[#]-#]==2&] (* Harvey P. Dale, Oct 13 2011 *)

Crossrefs

Sequence in context: A143788 A351686 A165459 * A272721 A089777 A050857

Adjacent sequences: A108791 A108792 A108793 * A108795 A108796 A108797

Keyword

easy,nonn,base

Author

Jason Earls, Jul 09 2005

Status

approved