Concatenation of sequences (1,2,...,n-1,n,n-1,...,2) for n >= 2.

Terms

a(0) =1a(1) =2a(2) =1a(3) =2a(4) =3a(5) =2a(6) =1a(7) =2a(8) =3a(9) =4a(10) =3a(11) =2a(12) =1a(13) =2a(14) =3a(15) =4a(16) =5a(17) =4a(18) =3a(19) =2a(20) =1a(21) =2a(22) =3a(23) =4a(24) =5a(25) =6a(26) =5a(27) =4a(28) =3a(29) =2