ODE No. 1022

$$y(x)(a\cos (2x)+b)+y^{″}(x)=0$$ ✓ Mathematica : cpu = 0.0186718 (sec), leaf count = 28

DSolve[(b + a*Cos[2*x])*y[x] + Derivative[2][y][x] == 0,y[x],x]
 

$$\left\{\{y(x)\to c_1\text{MathieuC}[b,-\frac{a}{2},x]+c_2\text{MathieuS}[b,-\frac{a}{2},x]\}\right\}$$ ✓ Maple : cpu = 0.2 (sec), leaf count = 21

dsolve(diff(diff(y(x),x),x)+(a*cos(2*x)+b)*y(x)=0,y(x))
 

$$y\left(x\right)=c_1\mathrm{MathieuC}(b,-\frac{a}{2},x)+c_2\mathrm{MathieuS}(b,-\frac{a}{2},x)$$