Final digit of triangular number n*(n+1)/2.

Terms

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