Update ncsf.py documentation

[0-andy-0]

Correction lines 184-189: Psi is not the tensor algebra on the primitives but on the generators of this free Lie algebra.

Correction lines 184-189: Psi is not the tensor algebra on the primitives but on the generators of this free Lie algebra.

Fixes #38370

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[fchapoton]

looks good, thanks

[fchapoton]

thanks for removing the spaces

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[0-andy-0]

thanks for removing the spaces

Glad to help! Just a remark, I think I know how the error occured: probably modelled too closely on the documentation for the symmetric functions:

The graded connected bialgebra of symmetric functions over a algebra has a rather simply-understood structure: It is (isomorphic to) the symmetric algebra of its space of primitives

which is correct as the primitives are an abelian Lie algebra here 😄