@InProceedings{   senizergues:hal-00368266,
  Author        = "S{\'e}nizergues, G{\'e}raud",
  Abstract      = "{Sequences of numbers (either natural integers, or integers or rational) of level $k \in \bbbn$ have been defined in \cite{Fra-Sen06} as the sequences which can be computed by deterministic pushdown automata of level $k$. We extend this definition to sequences of {\em words} indexed by {\em words}. We give characterisations of these sequences in terms of ``higher-order'' L-systems. In particular sequences of rational numbers of level 3 are characterised by polynomial recurrences (which generalize the P-recurrent sequences studied in \cite{Sta80}). The equality problem for sequences of rational numbers of level 3 is shown decidable.}",
  Address       = "Yekaterinburg, Russie, F{\'e}d{\'e}ration De",
  affiliation   = "Laboratoire Bordelais de Recherche en Informatique - LaBRI",
  audience      = "internationale",
  BookTitle     = "{Proceedings CSR'07}",
  date-added    = "2014-01-01 22:51:22 +0000",
  date-modified = "2014-01-01 22:51:22 +0000",
  hal_id        = "hal-00368266",
  Keywords      = "Iterated pushdown automata ;recurrent sequences ;equivalence problems.",
  Language      = "Anglais",
  Pages         = "24-32",
  Publisher     = "Springer",
  Title         = "{Sequences of level $1, 2, 3,\ldots, k,\ldots$}",
  URL           = "http://hal.archives-ouvertes.fr/hal-00368266",
  Volume        = "4649",
  Year          = "2007",
  bdsk-url-1    = "http://hal.archives-ouvertes.fr/hal-00368266",
  File          = "Sequences of level-paper\_csr07 - a - a - s.pdf",
  file-2        = "talk\_csr07 (0) (0) - a - a - s.pdf",
  file-3        = "paper\_csr07 (0) (0) - a - a - s.ps"
}

@InProceedings{ senizergues:hal-00368266, Author = "S{\'e}nizergues, G{\'e}raud", Abstract = "{Sequences of numbers (either natural integers, or integers or rational) of level $k \in \bbbn$ have been defined in \cite{Fra-Sen06} as the sequences which can be computed by deterministic pushdown automata of level $k$. We extend this definition to sequences of {\em words} indexed by {\em words}. We give characterisations of these sequences in terms of ``higher-order'' L-systems. In particular sequences of rational numbers of level 3 are characterised by polynomial recurrences (which generalize the P-recurrent sequences studied in \cite{Sta80}). The equality problem for sequences of rational numbers of level 3 is shown decidable.}", Address = "Yekaterinburg, Russie, F{\'e}d{\'e}ration De", affiliation = "Laboratoire Bordelais de Recherche en Informatique - LaBRI", audience = "internationale", BookTitle = "{Proceedings CSR'07}", date-added = "2014-01-01 22:51:22 +0000", date-modified = "2014-01-01 22:51:22 +0000", hal_id = "hal-00368266", Keywords = "Iterated pushdown automata ;recurrent sequences ;equivalence problems.", Language = "Anglais", Pages = "24-32", Publisher = "Springer", Title = "{Sequences of level $1, 2, 3,\ldots, k,\ldots$}", URL = "http://hal.archives-ouvertes.fr/hal-00368266", Volume = "4649", Year = "2007", bdsk-url-1 = "http://hal.archives-ouvertes.fr/hal-00368266", File = "Sequences of level-paper_csr07 - a - a - s.pdf", file-2 = "talk_csr07 (0) (0) - a - a - s.pdf", file-3 = "paper_csr07 (0) (0) - a - a - s.ps" }