Add/multiply sequence, see example.

Terms

a(0) =1a(1) =3a(2) =7a(3) =11a(4) =27a(5) =33a(6) =69a(7) =77a(8) =141a(9) =151a(10) =251a(11) =263a(12) =407a(13) =421a(14) =617a(15) =633a(16) =889a(17) =907a(18) =1231a(19) =1251a(20) =1651a(21) =1673a(22) =2157a(23) =2181a(24) =2757a(25) =2783a(26) =3459a(27) =3487a(28) =4271a(29) =4301