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## Re: [Axiom-mail] sum()

**From**: |
Daniel Yokomiso |

**Subject**: |
Re: [Axiom-mail] sum() |

**Date**: |
Tue, 22 Jun 2004 12:00:35 -0300 |

On Tue, 22 Jun 2004 08:59:04 +0000, Martin Rubey <martin> escreveu:
>* De: Martin Rubey <martin>*
>* Data: Tue, 22 Jun 2004 08:59:04 +0000*
>* Para: Marcus Better <marcusb>*
>* Assunto: Re: [Axiom-mail] sum()*
>* *
>* You tried: *
>* *
>* > f: Integer -> Integer;*
>* > f(0)==1; f(1)==2;*
>* > f(n)==sum(f(i)*f(n-i), i=0..(n-1))*
>* *
>* Try*
>* *
>* f: Integer -> Integer; *
>* f(0)==1; f(1)==2; *
>* f(n)==reduce(+,[f(i)*f(n-i) for i in 1..(n-1)])*
>* *
>* I have no good explanation why sum won't work.*
"sum" doesn't work because your definition is different. The original has "i"
ranging from 0 to (n - 1), while yours ranges from 1 to (n - 1). Using "i" from
0 makes the definition incorrect.
>* (Well, I know why it happens*
>* internally. I'm looking for a solution...)*
>* *
>* Martin*
Best regards,
Daniel Yokomizo.