[tex]Consider \: the \: sequence \: u_{n} \\ u_{n} \: appears \: to \: be \: arithmtic[/tex]
Quick Proof:
[tex]u_{4}-u_{3}=u_{3}-u_{2}=... \\ 19 - 13 = 13 - 7 = .. \\ 6 = 6 = ...[/tex]
[tex]u_{n} \: is \: arithmetic \: with \: d = 6 \:and \: u_{1} = 1 \\ [/tex]
[tex]u_{n} = u_{1}+(n-1)d \\ u_{100} = 1 + (100 - 1)6 \\ u_{100} = 595[/tex]
