3, 4, 16, 75, 366, 1945, 11886

The given series is in the below pattern,
First term = 3
Second term = First term x 1 +1³
⇒ Second term = 3 x 1 + 1³ = 3 + 1 = 4
Third term = Second term x 2 + 2³
⇒ Third term = 4 x 2 + 2³ = 8 + 8 = 16
Fourth term = Third term x 3 + 3³
⇒ Fourth term = 16 x 3 + 3³ = 48 + 27 = 75
Fifth term = Fourth term x 4 +4³
⇒ Fifth term = 75 x 4 + 4³ = 300 + 64 = 364
So 366 is wrong. we get 364 as 5th term.
Sixth term = Fifth term x 5 + 5³
⇒ Sixth term = 364 x 5 + 5³ = 1820 + 125 = 1945
Seventh term = Sixth term x 6 + 6³
⇒ Seventh term = 1945 x 6 + 6³ = 11670 + 216 = 11886