a(n) = a(n-1) + a(n-2) + n + 2 with n>1, a(0)=1, a(1)=2.

Terms

a(0) =1a(1) =2a(2) =7a(3) =14a(4) =27a(5) =48a(6) =83a(7) =140a(8) =233a(9) =384a(10) =629a(11) =1026a(12) =1669a(13) =2710a(14) =4395a(15) =7122a(16) =11535a(17) =18676a(18) =30231a(19) =48928a(20) =79181a(21) =128132a(22) =207337a(23) =335494a(24) =542857a(25) =878378a(26) =1421263a(27) =2299670a(28) =3720963a(29) =6020664