a(n) is the least semiprime > a(n-2) + a(n-1), with a(1) = 4 and a(2) = 6.

Terms

a(0) =4a(1) =6a(2) =14a(3) =21a(4) =38a(5) =62a(6) =106a(7) =169a(8) =278a(9) =451a(10) =731a(11) =1186a(12) =1919a(13) =3106a(14) =5027a(15) =8135a(16) =13165a(17) =21302a(18) =34473a(19) =55779a(20) =90253a(21) =146035a(22) =236291a(23) =382327a(24) =618622a(25) =1000951a(26) =1619581a(27) =2620538a(28) =4240121a(29) =6860662