Sipser, Michael Introduction to the theory of computation. (English) Zbl 1169.68300 Boston, MA: PWS Publishing (ISBN 0-534-94728-X). xv, 396 p. (1997). Cited in 258 Documents MSC: 68-01 Introductory exposition (textbooks, tutorial papers, etc.) pertaining to computer science 68Q05 Models of computation (Turing machines, etc.) (MSC2010) 68Q15 Complexity classes (hierarchies, relations among complexity classes, etc.) 68W05 Nonnumerical algorithms PDFBibTeX XMLCite \textit{M. Sipser}, Introduction to the theory of computation. Boston, MA: PWS Publishing (1997; Zbl 1169.68300) Online Encyclopedia of Integer Sequences: Number of length n words on alphabet {0,1,2} of the form 0^(i)1^(j)2^(k) such that i=j or j=k. Number of length n strings on the alphabet {0,1,2} of the form 0^i 1^j 2^k such that i,j,k>=0 and if i=1 then j=k.