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### Defining 4jm Wigner symbols

Hi everyone,

I am a neophyte and I can't understand my error in spite of the many tutorials I have watched. I want to define the 4jm Wigner symbols, which should basically be defined as:

var('m')
wigner_4j(j1,j2,j3,j4,j,m1,m2,m3,m4) = sum(wigner_3j(j1,j2,j,m1,m2,m)*wigner_3j(j,j3,j4,-m,m3,m4),m,-j,j)


I get plenty of errors that I can't fix. It is weird to me because the overall logic seemed good, as it works for instance when I define in a similar manner:

var('n')
b(p,q) = sum(binomial(p,n)*binomial(q,n),n,0,min(p,q))