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Gap Sequence of Factors of Fibonacci Sequence

Let w be a factor of Fibonacci sequence F=x_1x_2..., then it appears in the sequence infinitely many times. Let w_p be the p-th appearance of w and v_{w,p} be the gap between w_p and w_{p+1}. In this paper, we discuss the structure of the gap sequence {v_{w,p}}, we first introduce the singular kernel word sk(w) for any factor w of F and give a decomposition of w with respect to sk(w). Using the singular kernel and the decomposition, we prove the gap sequence {v_{w,p}} has exactly two different elements {v_{w,1},v_{w,2}} and determine the expressions of gaps completely, then we prove that the gap sequence over the alphabet {v_{w,1},v_{w,2}} is still a Fibonacci sequence. Finally, we introduce the spectrum for studying some typical combinatorial, using the results above, we determine completely the spectrums.