Starting from the fourth term, each term is the sum of the three preceding terms.
The next term is 6+3+2 = 11
It is also correct to say that, starting from the fourth term, each term is the sum of all preceding numbers.
By that rule, the next term is 6+3+2+1 = 12.
A sequence can have many different rules, as long as they work with the given numbers.
This is also the numbers for the Baxter Permutations (Sloane's Sequence. 0,1,2,3,6,22... in which case 22 is the next number.
This is also the sequence of n such that 90*n + 47 is a prime number, in which case the next number in the sequence is 7.