What comes next in the pattern 3 -6 12 4 20?

The pattern alternates between two sequences. The first sequence is multiplying by 2 (3 to 6, then 6 to 12), while the second sequence adds 1 and then multiplies by 5 (4 to 20). Following this pattern, after 20, the next term in the first sequence would be 12 multiplied by 2, which is 24. Therefore, the next number in the pattern is 24.