PASCALMATRIX
=LAMBDA(n,
    LAMBDA(f,
        LET(
            ixs, SEQUENCE(n, n, 0, 1),

            f(BINCOEFF)(
                QUOTIENT(ixs, n)
            )(
                MOD(ixs, n)
            )
        )
    )
)


BINCOEFF
=LAMBDA(n,
    LAMBDA(k,
        IF(n < k,
            0,
            QUOTIENT(FACT(n), FACT(k) * FACT(n - k))
        )
    )
)


SYMMETRIC
=LAMBDA(f,
    LAMBDA(a,
        LAMBDA(b,
            f(a + b)(b)
        )
    )
)