a(n) + a(n-1) = n-th prime.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =7a(6) =6a(7) =11a(8) =8a(9) =15a(10) =14a(11) =17a(12) =20a(13) =21a(14) =22a(15) =25a(16) =28a(17) =31a(18) =30a(19) =37a(20) =34a(21) =39a(22) =40a(23) =43a(24) =46a(25) =51a(26) =50a(27) =53a(28) =54a(29) =55