  Cauchy summation formula plays a central role in application of character
calculus to many problems, from AGT-implied Nekrasov decomposition of conformal
blocks to topological-vertex decompositions of link invariants. We briefly
review the equivalence between Cauchy formula and expressibility of skew
characters through the Littlewood-Richardson coefficients. As
not-quite-a-trivial illustration we consider how this equivalence works in the
case of plane partitions -- at the simplest truly interesting level of just
four boxes.
