%I #6 Jun 14 2015 16:26:09
%S 313,717,1323,1929,3141,3747,4353,6171,7383,7989,97107,103113,127137,
%T 139149,157167,163173,181191,223233,229239,241251,271281,283293,
%U 307317,337347,349359,373383,379389,409419,421431,433443,439449,457467,499509
%N Concatenations of pairs of primes that differ by 10.
%C There are no primes in this sequence after a(1) = 313, as all values thereafter are divisible by 3. Semiprimes in this sequence include: a(2) = 717 = 3 * 239, a(4) = 1929 = 3 * 643, a(6) = 3747 = 3 * 1249, a(7) = 4353 = 3 * 1451, a(10) = 7989 = 3 * 2663, a(11) = 97107 = 3 * 32369, a(13) = 127137 = 3 * 42379, a(17) = 181191 = 3 * 60397, a(18) = 223233 = 3 * 74411, a(29) = 421431 = 3 * 140477, a(30) = 433443 = 3 * 144481, a(34) = 547557 = 3 * 182519, a(35) = 577587 = 3 * 192529, a(40) = 691701 = 3 * 230567, a(41) = 709719 = 3 * 236573, a(49) = 919929 = 3 * 306643, a(52) = 10091019 = 3 * 3363673.
%H Harvey P. Dale, <a href="/A104719/b104719.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = A023203(n) concatenated with A023203(n)+10.
%e Primes 3 and 13 differ by 10.
%t FromDigits[Join[IntegerDigits[#],IntegerDigits[#+10]]]&/@Select[ Prime[ Range[ 100]], PrimeQ[ #+10]&] (* _Harvey P. Dale_, Jun 14 2015 *)
%Y Cf. A000040, A001358, A023202, A103195, A103206, A104718.
%K base,easy,nonn
%O 1,1
%A _Jonathan Vos Post_ and _Parthasarathy Nambi_, Mar 20 2005