bca _ b _ aabc __ a __ caa

The series is ccc bbb aaa/ccc bbb aaa/c. Thus, the pattern ccc bbb aaa is repeated.

The series is abb/abb/abb/abb. Thus, the pattern 'abb' is repeated.

The series is abncb/abncb/abncb. Thus, the pattern 'abncb' is repeated.

The series is nnmm/nnmn/nnmm/nnmm. Thus, the pattern 'nnmm' is repeated.

The series is abb/aaabbb/aaaabbbb/a. Thus the letters are repeated twice, then thrice, then four times and so on.

The series is abadna/abadna/abadna/ab. Thus, the pattern 'abadna' is repeated.

The series is man/man/man/man/man. Thus, the pattern 'man' is repeated.

The series is bbccaa/ccaabb/aabbcc. Thus, the letter pairs move in a cyclic order.

The series is mopn/mopn/mopn/mopn. Thus, the pattern 'mopn' is repeated.