1 together with positive even numbers.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =8a(5) =10a(6) =12a(7) =14a(8) =16a(9) =18a(10) =20a(11) =22a(12) =24a(13) =26a(14) =28a(15) =30a(16) =32a(17) =34a(18) =36a(19) =38a(20) =40a(21) =42a(22) =44a(23) =46a(24) =48a(25) =50a(26) =52a(27) =54a(28) =56a(29) =58