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

Terms

a(0) =1a(1) =1a(2) =4a(3) =8a(4) =16a(5) =29a(6) =51a(7) =87a(8) =146a(9) =242a(10) =398a(11) =651a(12) =1061a(13) =1725a(14) =2800a(15) =4540a(16) =7356a(17) =11913a(18) =19287a(19) =31219a(20) =50526a(21) =81766a(22) =132314a(23) =214103a(24) =346441a(25) =560569a(26) =907036a(27) =1467632a(28) =2374696a(29) =3842357