sumExpand

◼ sumExpand[expr] expands sums in expr over the addends.

◼ sumExpand also expands within addends using ExpandAll.

◼ See also: sum, sumThread, sumFullSimplify, sumCollect, sumSimplifyKD, sumAbstractIndex, sumNameIndex.

Further examples

Load sneg and declare some quantities.

<< sneg`sneg`;
snegfermionoperators[c]
snegfreeindexes[k, σ]

Expands the argument of the sum

sum[number[c[k]], {k}]
sumExpand[%]

Expands the added, the expands over the expanded arguments

sum[f[k] (number[c[k]] - 1), {k}]
sumExpand[%]