Recurrence Relations
A recurrence relation is an equation that recursively defines a sequence. Each term of the sequence is defined as a function of preceding terms.
| Recurrence relation | How the next term is obtained | First terms |
|---|---|---|
| \(x_{n+1}=\sqrt{x_n+5},\ x_0=1\) | Add \(5\), then take the positive square root. | \(1,\sqrt6,\sqrt{\sqrt6+5},\ldots\) |
| \(u_{n+1}=0.5u_n+8,\ u_1=4\) | Halve the current term, then add \(8\). | \(4,10,13,14.5,15.25,\ldots\) |
| \(a_n=a_{n-1}+k,\ a_0=3\) | Add the constant \(k\). | \(3,3+k,3+2k,3+3k,\ldots\) |
| \(u_n=-2u_{n-1},\ u_0=3\) | Multiply the current term by \(-2\). | \(3,-6,12,-24,48,\ldots\) |
| \(T_n=T_{n-1}+T_{n-2},\ T_1=0,\ T_2=1\) | Add the preceding two terms. | \(0,1,1,2,3,\ldots\) |
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