Find the n th term and sum of n terms of the series 5 + 8 + 17 + 44 ..........

Question

Find the n th term and sum of n terms of the series  5 + 8 + 17 + 44 ..........

anonymous · Answer

Ah, this is a nice series. 
$$[5,8,17,44]$$

experimentx · Answer

find the difference .. note the difference in the difference is a multiple of 3

anonymous · Answer

Yes the first order difference is in Gp

anonymous · Answer

and on...so do as @experimentX suggests, first examine any sort of relationship that could exist, you see that each termer is greater than the next

anonymous · Answer

I suggest that you show us the values you have for the difference between the numbers in the series

anonymous · Answer

Once, you have those differences, see if there is a pattern or relationship among them

zepp · Answer

Looks like 3 to some power :D

experimentx · Answer

tn+1 = tn + 3^(n-1)

anonymous · Answer

term1 = 5    
term2 = 8     term2 - term1 = 3   so term2 = term1 + 3
term3 = 17   term3 - term2 = 9   so term3 = term2 + 9
term4 = 44   term5 - term4 = 27 so term4 = term3 + 27
term5 = ...

experimentx · Answer

don't know closed form at the moment!!

anonymous · Answer

So @Yahoo! How are you doing with this?

anonymous · Answer

Ar^n + b1n^k-1 + b2n^k-2............bk

anonymous · Answer

Hmm, can you explain the terms please?

anonymous · Answer

it is the general formula lol1

anonymous · Answer

ok
look at the sequence 
first term is (3^1+7)/2=5
second is  (3^2+7)/2=8
third is      (3^3+8)/2=17

can you now tell me general formula ?

experimentx · Answer

i guess we should use summation rule
|dw:1343147827410:dw|