Primes formed by concatenating n and 2n-1.

Terms

a(0) =11a(1) =23a(2) =47a(3) =59a(4) =1019a(5) =1223a(6) =1427a(7) =1733a(8) =2039a(9) =2141a(10) =2243a(11) =2447a(12) =2549a(13) =2753a(14) =2957a(15) =3467a(16) =3671a(17) =4079a(18) =4283a(19) =4691a(20) =4793a(21) =5099a(22) =52103a(23) =55109a(24) =61121a(25) =65129a(26) =70139a(27) =75149a(28) =77153a(29) =82163