CoolMyth - The question u posted is not under the H2 Maths
syllabus of neither Method of Differences nor
Summation of series nor simple
recurrence
Anyway Pi is an irrational number thus under your syallabus the
most complex way for expressing a funcation is only maclaurin
series thus i don't have the solution for your question.
Sry but pls ask only JC maths questions