The lesser of the 2^n-th twin prime pair (A001359).

Terms

a(0) =3a(1) =5a(2) =17a(3) =71a(4) =227a(5) =821a(6) =2087a(7) =5021a(8) =13757a(9) =33149a(10) =81197a(11) =186647a(12) =435401a(13) =1002719a(14) =2241779a(15) =5060171a(16) =11296421a(17) =25121207a(18) =55559507a(19) =121831601a(20) =266187827a(21) =578653919a(22) =1253242691a(23) =2705496551a(24) =5820833729a(25) =12491149637a(26) =26733605159a(27) =57077657321a(28) =121575837179a(29) =258438193379