We use the notations of Chap. VI, Plate II, in the case of an algebra of type B2. Let n,p be integers ≥0.
a) We have
P(nα1+p(α1+2α2))=1+21p(p+3)
P(nα2+p(α1+α2))=[p2/4]+p+1
P(n(α1+α2)+p(α1+2α2))=[n2/4]+n+1+np+21p(p+3)
b) Let λ=n(α1+α2)+p(α1+2α2). The multiplicity of the weight 0 in E(λ) is
[n/2]+1+np+p
Nothing.
Nothing.