Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 3247 by [email protected]: problem with summation() function,
simple problem it do not solve
http://code.google.com/p/sympy/issues/detail?id=3247
This is sympy from git as of 25.04.2012:
(Example from the book A=B)
In [42]: summation(
(-1)**(n+r+s)*binomial(n,r)*binomial(n,s)*binomial(n+r,r)*binomial(n+s,s)*binomial(2*n-r-s,n),(r,0,n),(s,0,n))
Out[42]:
n n
____ ____
╲ ╲
╲ ╲ n + r + s ⎛n⎞ ⎛n⎞ ⎛n + r⎞ ⎛n + s⎞ ⎛2⋅n - r - s⎞
╲ ╲ (-1) ⋅⎜ ⎟⋅⎜ ⎟⋅⎜ ⎟⋅⎜ ⎟⋅⎜ ⎟
╱ ╱ ⎝r⎠ ⎝s⎠ ⎝ r ⎠ ⎝ s ⎠ ⎝ n ⎠
╱ ╱
╱ ╱
‾‾‾‾ ‾‾‾‾
s = 0 r = 0
According to A=B this should have the same value as the following:
In [43]: summation( binomial(n,k)**4, (k,0,n))
Out[43]:
┌─ ⎛-n, -n, -n, -n │ ⎞
├─ ⎜ │ 1⎟
4╵ 3 ⎝ 1, 1, 1 │ ⎠
Kjetil
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