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

Terms

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