suivant: Sub-sequence of a sequence
précédent: Concat two sequences :
Table des matières
The elements of a sequence have indexes begining at 0 in Xcas
mode or 1 in other modes.
Get an element of a sequence : 
A sequence or a variable name assigned to a sequence
followed by [n] returns the element of index n of the sequence.
giac documentation written by Renée De Graeve and Bernard Parisse