Option variable
cauchysumDefault value: false
When multiplying together sums with inf as their upper limit,
if sumexpand is true and cauchysum is true
then the Cauchy product will be used rather than the usual
product.
In the Cauchy product the index of the inner summation is a
function of the index of the outer one rather than varying
independently.
Example:
(%i1) sumexpand: false$ (%i2) cauchysum: false$ (%i3) s: sum (f(i), i, 0, inf) * sum (g(j), j, 0, inf); inf inf ==== ==== \ \ (%o3) ( > f(i)) > g(j) / / ==== ==== i = 0 j = 0 (%i4) sumexpand: true$ (%i5) cauchysum: true$ (%i6) ''s; inf i1 ==== ==== \ \ (%o6) > > g(i1 - i2) f(i2) / / ==== ==== i1 = 0 i2 = 0