

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.


1



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
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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: A296806 A143788 A165459 * A272721 A089777 A050857
Adjacent sequences: A108791 A108792 A108793 * A108795 A108796 A108797


KEYWORD

easy,nonn,base


AUTHOR

Jason Earls, Jul 09 2005


STATUS

approved



