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23 Weierstrass Elliptic and Modular FunctionsWeierstrass Elliptic Functions

§23.9 Laurent and Other Power Series

Let z0(≠0) be the nearest lattice point to the origin, and define

23.9.1 cn=(2⁢n−1)⁢∑w∈𝕃∖{0}w−2⁢n,
n=2,3,4,….

Then

23.9.2 ℘⁡(z)=1z2+∑n=2∞cn⁢z2⁢n−2,
0<|z|<|z0|,
23.9.3 ζ⁡(z)=1z−∑n=2∞cn2⁢n−1⁢z2⁢n−1,
0<|z|<|z0|.

Here

23.9.4 c2 =120⁢g2⁡,
c3 =128⁢g3⁡,
23.9.5 cn=3(2⁢n+1)⁢(n−3)⁢∑m=2n−2cm⁢cn−m,
n≥4.

Explicit coefficients cn in terms of c2 and c3 are given up to c19 in Abramowitz and Stegun (1964, p. 636).

For j=1,2,3, and with ej⁡ as in §23.3(i),

23.9.6 ℘⁡(ωj+t)=ej⁡+(3⁢ej⁡2−5⁢c2)⁢t2+(10⁢c2⁢ej⁡+21⁢c3)⁢t4+(7⁢c2⁢ej⁡2+21⁢c3⁢ej⁡+5⁢c22)⁢t6+O⁡(t8),

as t→0. For the next four terms see Abramowitz and Stegun (1964, (18.5.56)). Also, Abramowitz and Stegun (1964, (18.5.25)) supplies the first 22 terms in the reverted form of (23.9.2) as 1/℘⁡(z)→0.

For z∈ℂ

23.9.7 σ⁡(z)=∑m,n=0∞am,n⁢(10⁢c2)m⁢(56⁢c3)n⁢z4⁢m+6⁢n+1(4⁢m+6⁢n+1)!,

where a0,0=1, am,n=0 if either m or n<0, and

23.9.8 am,n=3⁢(m+1)⁢am+1,n−1+163⁢(n+1)⁢am−2,n+1−13⁢(2⁢m+3⁢n−1)⁢(4⁢m+6⁢n−1)⁢am−1,n.

For am,n with m=0,1,…,12 and n=0,1,…,8, see Abramowitz and Stegun (1964, p. 637).