In the sequence: 2,5,3, starting with the third, each term is equal to the term preceeding it minus the term preceeding that one. What is the sum of the first 112 terms of this sequence?

Question

anonymous · Answer

2,5,3...........???

anonymous · Answer

is it a fibanocci sequence

anonymous · Answer

Sorta, its 2+5-3

anonymous · Answer

Then, 5+3-4

amistre64 · Answer

its prolly a telescoping sum

anonymous · Answer

Yup

amistre64 · Answer

a1+a2+a3+(a3-a2)+(a4-a3)+(a5-a4) + ...  +(a111 - a110)
        ^           ^    ^      ^   ^      ^   ^                               ^

looks to me like it would amount to:

a1+a3+a111  if you can determine those terms

anonymous · Answer

Okay

So 2+3+x

amistre64 · Answer

yep, only problem is in determining an explicit formula to find the nth term with :/

amistre64 · Answer

we could write a program to follow the rules set out to find it recurssively

anonymous · Answer

Okay like in sum notation?

amistre64 · Answer

i was thinking more like in "javascript"  :)

anonymous · Answer

Well I have a TI-84 + so I kinda want a program for it

amistre64 · Answer

i never learnt how to program those fancy things :/

anonymous · Answer

I can but I need the formula :P

amistre64 · Answer

might do the trick

anonymous · Answer

OMG

anonymous · Answer

I'll give you a medal for that :P

amistre64 · Answer

lol, lets see if it works :)

copy and past it into a textfile named, i dunno .... tryIt.html

anonymous · Answer

K

amistre64 · Answer

attachment

anonymous · Answer

I did it but what do I type into the box?

amistre64 · Answer

teh box is just a display; the button runs thru the recurrsive parts and stores each value into an array for calculating; all we need is the a111 value; hit the button and it should give you 3 in the box

anonymous · Answer

Okay but how did you learn how use javascript?

amistre64 · Answer

heres a better version of it that shows you the values as it calculates;

i learned it by going online and reading about it; there are sites that have all sorts of information that arent part of facebook, and have nothing to do with porn ....  lol

amistre64 · Answer

after the first nine terms it looks like a pattern would have become apparent

2 5 3 -2 -5 -3 2 5 3 etc ....