2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/130887For a prime number p, we construct a generating set for the ring of invariants for the p+1 dimensional indecomposable modular representation of a cyclic group of order p^2. We then use the constructed invariants to describe the decomposition of the symmetric algebra as a module over the group ring, confirming the Periodicity Conjecture of Ian Hughes and Gregor Kemper for this case.The revised version of the paper includes a calculation of the Noether number of the p+1 dimensional modular indecomposable representation of the cyclic group of order p^2 and the Hilbert series of the corresponding ring of invariantsCommutative AlgebraRepresentation Theory13A50text