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

Terms

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