read `Ising2D.txt`:

ope:=LarsDE(v,Dv):

print(`The linear recurrence operator annihilating the series of coefficients of the Onsager function, let's call it f(v)  is`):
print(``):
print(coeff(ope,Dv,0)*f(v) +add(coeff(ope,Dv,i)*diff(f(v),v$i),i=1..degree(ope,Dv) )=0):
print(``):
print(`and in Maple notation`):
print(``):
lprint(coeff(ope,Dv,0)*f(v) +add(coeff(ope,Dv,i)*diff(f(v),v$i),i=1..degree(ope,Dv) )=0):
print(``):
print(`the differential operator is`):
print(``):
lprint(ope):

quit: