The aim of this paper is to analyse the reasoning and symbolisations used by sixth grade Moroccan students in solving a task based on figurative patterns. Our analysis aims at identifying the systems of actions elaborated by the students to give the general expression of the sequence, according to their perceptions of the sequence of its patterns. The results of this study show that the students can produce a wide variety of generalisations, without using the letter, by resorting to verbal expressions, the majority of which remain in the class of a factual or contextual generalisation. However, several students were not able to determine the general term of the sequence in the question, through an expression that is detached from the context of the situation. This study also contributes to raising the consciousness of Moroccan teachers and researchers of mathematics didactics about the important role played by algebraic thinking, in particular the generalisation coming from an activity based on the figurative patterns, which generates several equivalent and meaningful numerical or algebraic expressions. This article also sheds light on ways for programme designers to enrich primary school curricula, by proposing arithmetic activities with algebraic potential, like the one proposed in our study.