This is an interleaved sequence. Odd positions (1st, 3rd, 5th, 7th) follow: 1, 3, 7, 13 where the differences increase by 2 each time (+2, +4, +6). Even positions (2nd, 4th, 6th, 8th) follow: 2, 4, 6, 8 which increase by 2 each time. The next two numbers are 13 and 8.