Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #13 Dec 28 2019 07:47:58
%S 11,13,311,313,131111,131113,313331,313333,1131131,1131133,3331331,
%T 3331333,3333131,3333133,3333311,3333313,111113111,111113113,
%U 113331311,113331313,331313111,331313113,331331111,331331113,333331331,333331333
%N Twin prime pairs using digits 1 and 3 only.
%C Both the members of the twin prime pairs are included.
%H Amiram Eldar, <a href="/A111070/b111070.txt">Table of n, a(n) for n = 1..10000</a>
%F a(2k) = a(2k-1) + 2.
%t s = Select[Flatten @ Table[FromDigits /@ Tuples[{1, 3}, k], {k, 1, 9}], And @@ PrimeQ[10 # + {1, 3}] &]; Flatten @ Transpose @ {10 s + 1, 10 s + 3} (* _Amiram Eldar_, Dec 28 2019 *)
%Y Cf. A001097, A001359, A006512.
%K base,nonn
%O 1,1
%A _Amarnath Murthy_, Jan 02 2006
%E Corrected and extended by _Farideh Firoozbakht_, Jan 05 2006