Frédéric Chapoton writes:
> Here is a try
>
> Z=species.SingletonSpecies()
> E2=species.SetSpecies(min=2)
> P=CombinatorialSpecies()
> S=CombinatorialSpecies()
> P.define(E2.composition(Z+S))
> S.define(E2.composition(Z+P))
> N=Z+P+S
>
> That seems to work :
It should! Warning however: the unla
Here is a try
Z=species.SingletonSpecies()
E2=species.SetSpecies(min=2)
P=CombinatorialSpecies()
S=CombinatorialSpecies()
P.define(E2.composition(Z+S))
S.define(E2.composition(Z+P))
N=Z+P+S
That seems to work :
sage: koko=N.generating_series().coefficients(8)
sage: [koko[i]*factorial(i) for i in
