# What is the formula to this math sequence: 1, 3, 7, 14?

I really need help with this all math geniuses help!

ASAP!!!

Update:

Thanks so much everyone-you really helped me out.

You guys are the best!

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• Anonymous

1, 3, 7, 14

The next four terms of the sequence are 25, 41, 63, 91

If you know the (n-1)th term and the nth term, the formula for the (n+1)th term, call it T(n+1), is:

T(n+1) = 2 * T(n) - T(n-1) + n

That is, to find the next term, double the last term, subtract the previous term, and add the number of the last term.

• Are you sure that's supposed to be a 14? I've seen this sequence in many textbooks and it's a 15 and the formula is 2x+1, so (1 x 2)+1 is 3, 3x2 +1 = 7, 7x2 + 1 = 15

• that doesn't look like it has an actual answer. are you sure it's not 15 instead of 14? 15 would make more sense and would give you an actual answer.

2x+1 would be your formula if it is 15.

if it's 14, then it's possible that the formula changes from 2x+1 to just 2x.

i place my bet on the last number being 15 though since it'd make sooooo much more sense

• 1*2=2+1=3 3*2=6+1=7 7*2=14...not sure the 14 really throws me off.