On Sun, Nov 18, 2012 at 9:02 PM, Shriramana Sharma <samj...@gmail.com>wrote:
> On Sun, Nov 18, 2012 at 8:16 PM, Shriramana Sharma <samj...@gmail.com>
> wrote:
> >
> > ...: summation(lamb[i]*(-1)**(n-j)*binomial(i,n-j),(i,n-j,n))
>
>
Something like this?
>>> var('i j n')
(i, j, n)
>>> lamb = Function('lamb')
>>> Sum(lamb(i)*(-1)**(n-j)*binomial(i,n-j),(i,n-j,n))
Sum((-1)**(-j + n)*lamb(i)*binomial(i, -j + n), (i, -j + n, n))
>>> _.subs(((i,3),(j,4)))
Sum((-1)**(n - 4)*lamb(i)*binomial(i, n - 4), (i, n - 4, n))
>>> _.subs(n,6)
Sum(i*(i - 1)*lamb(i)/2, (i, 2, 6))
>>> _.doit()
lamb(2) + 3*lamb(3) + 6*lamb(4) + 10*lamb(5) + 15*lamb(6)
>>>
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