1 | initial version |

Is the following what you need?

```
sage: f = function('f')
sage: g = function('g')
sage: R.<z> = PowerSeriesRing(SR)
sage: F = sum(f(i)*z^i for i in range(3)) + O(z^3)
sage: G = sum(g(i)*z^i for i in range(3)) + O(z^3)
sage: F*G
f(0)*g(0) + (f(0)*g(1) + f(1)*g(0))*z + (f(0)*g(2) + f(1)*g(1) + f(2)*g(0))*z^2 + O(z^3)
```

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