Let R be a graded A-ring. We extend a well-known formula in the universal ring of Witt vectors by replacing the power operations by the Adams operations. Our method provides us an easy way to compute the inverse image by the symmetric power operators of certain elements of R. As a corollary we get identities, found by Klyachko and Hanlon, in the rings 1 + Z [[t]] + and 1 + R [[t]] + , where R is the representation ring of the symmetric groups.In their work [1] Dress and Siebeneicher proved the Cyclotomic Identity (see [7]), which takes place in the ring 1 + Z[[*]] + , by using the Burnside ring and the universal ring of Witt vectors. The main result of this paper is to generalise this identity by proving a similar identity, which takes place in 1 + -R[[<]] + , where R is a A-ring. In this new setting the n-th power operation is replaced by the Adams operation \& n .This new formula permits us to give a quick proof of two results, one by Hanlon [3] and one by Klyachko [4], about the representations of the symmetric group associated to the free Lie algebra. Here the A-ring R is the representation ring of the symmetric groups © R(S n ) • In Section 1 we construct a diagram associated to any graded A-ring R, that leads us to find the inverse image by S = £) S* (S* denotes the symmetric power operator) of certain elements of R. We use elementary concepts and results of A-ring theory and some ideas of a nice construction of Dress-Siebeneicher (see [1]). In Section 2 we apply the results of Section 1 to the representation ring R = © -R(S n ).
PRIMITIVE ELEMENTS IN A A-RINGWe recall some classical notation and results. For complete definitions and proofs we refer to Knutson (see [5]).Let R be a torsion free graded A-ring, that is R = 0 R n is such that its Aoperations satisfy jR, n D X t (R n ), for i, n ^ 0. The ring R := ]\ R n has a natural A-ring structure, inherited from the one of R.