If a, b in sequence, so is ab+4.

Terms

a(0) =2a(1) =8a(2) =20a(3) =44a(4) =68a(5) =92a(6) =140a(7) =164a(8) =188a(9) =284a(10) =332a(11) =356a(12) =380a(13) =404a(14) =548a(15) =572a(16) =668a(17) =716a(18) =740a(19) =764a(20) =812a(21) =884a(22) =1100a(23) =1124a(24) =1148a(25) =1316a(26) =1340a(27) =1364a(28) =1436a(29) =1484