Luke (1975, pp. 416–421) gives Chebyshev-series expansions for Hn(x), Ln(x), 0≤|x|≤8, and Hn(x)-Yn(x), x≥8, for n=0,1; ∫0xt-mH0(t)dt, ∫0xt-mL0(t)dt, 0≤|x|≤8, m=0,1 and ∫0x(H0(t)-Y0(t))dt, ∫x∞t-1(H0(t)-Y0(t))dt, x≥8; the coefficients are to 20D.
MacLeod (1993) gives Chebyshev-series expansions for L0(x), L1(x), 0≤x≤16, and I0(x)-L0(x), I1(x)-L1(x), x≥16; the coefficients are to 20D.
Newman (1984) gives polynomial approximations for Hn(x) for n=0,1, 0≤x≤3, and rational-fraction approximations for Hn(x)-Yn(x) for n=0,1, x≥3. The maximum errors do not exceed 1.2×10⁻⁸ for the former and 2.5×10⁻⁸ for the latter.