\[ (2 a x+b) y'(x)+a y(x)+3 (2 x-1) y''(x)+2 (x-1) x y^{(3)}(x)=0 \] ✓ Mathematica : cpu = 60.2872 (sec), leaf count = 115
\[\left \{\left \{y(x)\to c_3 \text {MathieuC}\left [-\frac {a}{2}-\frac {b}{2}+1,\frac {a}{4},\cos ^{-1}\left (\sqrt {x}\right )\right ] \text {MathieuS}\left [-\frac {a}{2}-\frac {b}{2}+1,\frac {a}{4},\cos ^{-1}\left (\sqrt {x}\right )\right ]+c_1 \text {MathieuC}\left [-\frac {a}{2}-\frac {b}{2}+1,\frac {a}{4},\cos ^{-1}\left (\sqrt {x}\right )\right ]^2+c_2 \text {MathieuS}\left [-\frac {a}{2}-\frac {b}{2}+1,\frac {a}{4},\cos ^{-1}\left (\sqrt {x}\right )\right ]^2\right \}\right \}\] ✓ Maple : cpu = 0.996 (sec), leaf count = 79
\[ \left \{ y \left ( x \right ) ={\it \_C1}\, \left ( {\it MathieuC} \left ( -{\frac {a}{2}}-{\frac {b}{2}}+1,{\frac {a}{4}},\arccos \left ( \sqrt {x} \right ) \right ) \right ) ^{2}+{\it \_C2}\, \left ( {\it MathieuS} \left ( -{\frac {a}{2}}-{\frac {b}{2}}+1,{\frac {a}{4}},\arccos \left ( \sqrt {x} \right ) \right ) \right ) ^{2}+{\it \_C3}\,{\it MathieuC} \left ( -{\frac {a}{2}}-{\frac {b}{2}}+1,{\frac {a}{4}},\arccos \left ( \sqrt {x} \right ) \right ) {\it MathieuS} \left ( -{\frac {a}{2}}-{\frac {b}{2}}+1,{\frac {a}{4}},\arccos \left ( \sqrt {x} \right ) \right ) \right \} \]