a(n) = 39 - n.

Terms

a(0) =39a(1) =38a(2) =37a(3) =36a(4) =35a(5) =34a(6) =33a(7) =32a(8) =31a(9) =30a(10) =29a(11) =28a(12) =27a(13) =26a(14) =25a(15) =24a(16) =23a(17) =22a(18) =21a(19) =20a(20) =19a(21) =18a(22) =17a(23) =16a(24) =15a(25) =14a(26) =13a(27) =12a(28) =11a(29) =10