SUND[a, b, c]
are the symmetric .
Overview, SUNDelta, SUNF, SUNSimplify.
[a, b, c] SUND
[a, b, c, Explicit -> True] SUND
[c, a, b] SUND
[a, b, b] SUND
[SUND[a, b, c] SUND[a, b, c]] SUNSimplify
[SUND[a, b, c] SUND[a, b, c], SUNNToCACF -> False] // Factor2 SUNSimplify
[SUND[a, b, c] SUND[e, b, c], SUNNToCACF -> False] // Factor2 SUNSimplify
[a, b, c] // StandardForm
SUND
(*SUND[a, b, c]*)
[a, b, c] // FCI // StandardForm
SUND
(*SUND[SUNIndex[a], SUNIndex[b], SUNIndex[c]]*)
[a, b, c] // FCI // FCE // StandardForm
SUND
(*SUND[a, b, c]*)