What is the general formula for how the following numbers are ordered: 1, 13, 31, 57, 77, 131, 171, -77

Question

anonymous · Answer

@myininaya Here's the question, sorry I forgot a part of it so I edited it :P

myininaya · Answer

is that last number really -77?

anonymous · Answer

Yea lol

anonymous · Answer

A friend asked me a question and I cannot seem to get it at all

anonymous · Answer

im not sure there is a formula for it

anonymous · Answer

He added more to it too: What is the general formula for how the following numbers are ordered: 1, 13, 31, 57, 77, 131, 171, -77, -121, 1127 ...

anonymous · Answer

just simple mathematics

anonymous · Answer

there is no formula

anonymous · Answer

-121, -77, 1, 13, 57, 77, 131, 171, 1127...

anonymous · Answer

I'm having a kind of a brain toot right now :/

anonymous · Answer

???

myininaya · Answer

lol I was trying to make a recurrence relation 
I played with first 7 terms to get the 8th term
but the recurrence didn't work for the 9th term

anonymous · Answer

He said the numbers are in the correct spot in the question stated

myininaya · Answer

$$a_7=-(a_6-a_5)-(a_4-a_3)-(a_2-a_1)+a_0 \ \text{ but } \a_8 \neq -(a_7-a_6)-(a_5-a_4)-(a_3-a_2)+a_1$$

myininaya · Answer

did he give any hint?

anonymous · Answer

He just said it doesn't require a calculator and being good at math is helpful but isn't required for solving

anonymous · Answer

But I'm tired and full of anxiety right now and I am unsure why he is asking me this question right now, lol.

anonymous · Answer

Well, thank you anyway. I'm just going to drop it. Thanks :)

myininaya · Answer

i would like to know what formula/equation thingy he was using if you ever find out