Binomial in a Summation

david8381
23 ●4 ●5 ●8

sage: var('k')

sage: sum(binomial(5,k),k,0,5)

I get an error "cannot convert k to int"

But if instead I try something like sum(binomial(n,k),k,0,n), everything is just fine.

Anyone know how I can get around this?

1 Answer

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calc314
4191 ●22 ●48 ●113

Sum is working only in a symbolic ring. So you can convert your integers to the symbolic ring as follows:

sum(binomial(SR(5),k),k,0,SR(5))

You can also use the add command:

add([binomial(5,k) for k in [0..5]])

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Asked: 11 years ago

Seen: 1,463 times

Last updated: Jul 25 '13