Find two linearly independent solutions of $y'' + 3 xy = 0$ of the form

$y_1 = 1 + a_3 x^3 + a_6 x^6 + \cdots$

$y_2 = x + b_4 x^4 + b_7 x^7 + \cdots$

Enter the first few coefficients:

$a_3 =$
$a_6 =$

$b_4 =$
$b_7 =$