Recurrence Formula for 3,5,13,27,55,...

In summary, the recurrence formula for the sequence 3,5,13,27,55,... is a<sub>n</sub> = 2a<sub>n-1</sub> + a<sub>n-2</sub>, where a<sub>n</sub> represents the nth term in the sequence. It is derived by observing the pattern in the sequence and can be used to find any term by plugging in the appropriate values for n. However, it is not the only way to generate the sequence, as a closed-form formula a<sub>n</sub> = 2<sup>n</sup> - 1 can also be used. Recurrence formulas can be applied to other sequences as long as there
  • #1
intervoxel
195
1
What is the recurrence formula for the sequence

[3,5,13,27,55,...]

Thank you for any help.
 
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  • #3
mfb said:
There is an infinite set of formulas that lead to this sequence.
Unless you made a typo, all of them are somewhat ugly.
You are right. It is 6 instead of 5. Thank you for the valuable link.
 

1. What is the recurrence formula for the sequence 3,5,13,27,55,...?

The recurrence formula for this sequence is an = 2an-1 + an-2, where an represents the nth term in the sequence. This means that each term is equal to twice the previous term plus the term before that.

2. How is the recurrence formula derived for this sequence?

The recurrence formula is derived by observing the pattern in the sequence. Each term is the sum of the two previous terms multiplied by 2. This can be expressed in the form of an = 2an-1 + an-2, which is the general form for a recurrence formula.

3. Can the recurrence formula be used to find any term in the sequence?

Yes, the recurrence formula can be used to find any term in the sequence by plugging in the appropriate values for n. For example, to find the 7th term, we would substitute n = 7 into the formula and solve for a7.

4. Is the recurrence formula the only way to generate this sequence?

No, there are other ways to generate this sequence. For example, we could use a closed-form formula, which is an explicit equation that gives the value of any term in the sequence without having to rely on previous terms. In this case, the closed-form formula for the sequence is an = 2n - 1.

5. Can the recurrence formula be used for other sequences?

Yes, the recurrence formula can be used for other sequences. It is a general form that can be applied to many different types of sequences, as long as there is a pattern that can be described by a formula. Recurrence formulas are commonly used in mathematics, computer science, and other scientific fields.

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