Let \( (1 + x + 2x^2)^{20} = a_0 + a_1 x + a_2 x^2 + \ldots + a_{40}x^{40} \). Then, \( a_1 + a_3 + a_5 + \ldots + a_{37} \) is equal to:
\( 2^{19}(2^{20} - 21) \)
\( 2^{19}(2^{20} + 21) \)
\( 2^{20}(2^{20} - 21) \)
\( 2^{20}(2^{20} + 21) \)