\[ \boxed { \left ( 2\,x+1 \right ) ^{2}{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) -2\, \left ( 2\,x+1 \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) -12\,y \left ( x \right ) -3\,x-1=0} \]
Mathematica: cpu = 0.044506 (sec), leaf count = 47 \[ \left \{\left \{y(x)\to c_1 (2 x+1)^3+\frac {c_2}{2 x+1}+\frac {-72 x^2-56 x-7}{192 (2 x+1)}\right \}\right \} \]
Maple: cpu = 0.016 (sec), leaf count = 42 \[ \left \{ y \left ( x \right ) ={\frac {{\it \_C1}}{2\,x+1}}+ \left ( 2\,x +1 \right ) ^{3}{\it \_C2}-{\frac {72\,{x}^{2}+56\,x+7}{384\,x+192}} \right \} \]