Twin lucky numbers (middle terms).

Terms

a(0) =2a(1) =8a(2) =14a(3) =32a(4) =50a(5) =68a(6) =74a(7) =128a(8) =134a(9) =170a(10) =194a(11) =236a(12) =260a(13) =284a(14) =320a(15) =392a(16) =428a(17) =476a(18) =488a(19) =518a(20) =536a(21) =578a(22) =614a(23) =620a(24) =644a(25) =728a(26) =740a(27) =884a(28) =896a(29) =926