Hi there!
I wanted to integrate a second order nonlinear differential equation,
and fricas responded with the error "no a linear diffeq"... Is just the
error message misleading, or is it a bug?
(I admit that I'd be positively surprised if it would have an elementary
integral...)
Martin
(1) -> D := series([(1/(n+1)*binomial(2*n, n))^2 for n in 0..])$UFPS FRAC POLY
INT;
Type: UnivariateFormalPowerSeries(Fraction(Polynomial(Integer)))
(2) -> P := 1 - recip D;
Type: UnivariateFormalPowerSeries(Fraction(Polynomial(Integer)))
(3) -> Da := recip(1-a*P);
Type: Union(UnivariateFormalPowerSeries(Fraction(Polynomial(Integer))),...)
(4) -> )expose RECOP
RecurrenceOperator is now explicitly exposed in frame frame1
(4) -> eq := getEq first guessADE([Da.i for i in 0..50])
(4)
2 3 2 2 3 2 ,,
(((16a - 16a)x + (- a + a)x )f(x) + 16a x - a x )f (x)
+
2 3 2 2 , 2
((- 32a + 32a)x + (2a - 2a)x )f (x)
+
2 2 2 2 ,
(((32a - 32a)x + (- 3a + 3a)x)f(x) + 32a x - 3a x)f (x)
+
3 2 2 3 2 2 2
((4a - 8a + 4a)x - a + 2a - 1)f(x) + ((8a - 8a)x + a - 4a + 3)f(x)
+
(4a x + 2a - 3)f(x) + 1
Type: Expression(Integer)
(5) -> f := operator 'f;
Type: BasicOperator
(6) -> solve(eq, f, x)
>> Error detected within library code:
parseLODE: not a linear ordinary differential equation
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