FIBONACCI AND CATALAN NUMBERS FIBONACCI AND CATALAN NUMBERS AN INTRODUCTION Ralph P. Grimaldi Rose-Hulman Institute of Technology Copyright©2012byJohnWiley&Sons,Inc.Allrightsreserved PublishedbyJohnWiley&Sons,Inc.,Hoboken,NewJersey PublishedsimultaneouslyinCanada Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformor byanymeans,electronic,mechanical,photocopying,recording,scanning,orotherwise,exceptas permittedunderSection107or108ofthe1976UnitedStatesCopyrightAct,withouteithertheprior writtenpermissionofthePublisher,orauthorizationthroughpaymentoftheappropriateper-copyfeeto theCopyrightClearanceCenter,Inc.,222RosewoodDrive,Danvers,MA01923,(978)750-8400,fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should beaddressedtothePermissionsDepartment,JohnWiley&Sons,Inc.,111RiverStreet,Hoboken,NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission. LimitofLiability/DisclaimerofWarranty:Whilethepublisherandauthorhaveusedtheirbesteffortsin preparingthisbook,theymakenorepresentationsorwarrantieswithrespecttotheaccuracyor completenessofthecontentsofthisbookandspecificallydisclaimanyimpliedwarrantiesof merchantabilityorfitnessforaparticularpurpose.Nowarrantymaybecreatedorextendedbysales representativesorwrittensalesmaterials.Theadviceandstrategiescontainedhereinmaynotbesuitable foryoursituation.Youshouldconsultwithaprofessionalwhereappropriate.Neitherthepublishernor authorshallbeliableforanylossofprofitoranyothercommercialdamages,includingbutnotlimitedto special,incidental,consequential,orotherdamages. Forgeneralinformationonourotherproductsandservicesorfortechnicalsupport,pleasecontactour CustomerCareDepartmentwithintheUnitedStatesat(800)762-2974,outsidetheUnitedStatesat(317) 572-3993orfax(317)572-4002. Wileyalsopublishesitsbooksinavarietyofelectronicformats.Somecontentthatappearsinprintmay notbeavailableinelectronicformats.FormoreinformationaboutWileyproducts,visitourwebsiteat www.wiley.com. LibraryofCongressCataloging-in-PublicationData: Grimaldi,RalphP. Fibonacciandcatalannumbers:anintroduction/RalphP.Grimaldi. p.cm. Includesbibliographicalreferencesandindex. ISBN978-0-470-63157-7 1. Fibonaccinumbers. 2. Recurrentsequences(Mathematics) 3. Catalannumbers (Mathematics) 4. Combinatorialanalysis. I. Title. QA241.G7252012 512.7’2–dc23 2011043338 PrintedintheUnitedStatesofAmerica 10 9 8 7 6 5 4 3 2 1 Dedicated to the Memory of Josephine and Joseph and Mildred and John and Madge CONTENTS PREFACE xi PARTONE THEFIBONACCINUMBERS 1. HistoricalBackground 3 2. TheProblemoftheRabbits 5 3. TheRecursiveDefinition 7 4. PropertiesoftheFibonacciNumbers 8 5. SomeIntroductoryExamples 13 6. CompositionsandPalindromes 23 7. Tilings:DivisibilityPropertiesoftheFibonacciNumbers 33 8. ChessPiecesonChessboards 40 9. Optics,Botany,andtheFibonacciNumbers 46 10. SolvingLinearRecurrenceRelations:TheBinetFormforF 51 n 11. Moreonαandβ:ApplicationsinTrigonometry,Physics,Continued Fractions,Probability,theAssociativeLaw,andComputerScience 65 12. ExamplesfromGraphTheory:AnIntroductiontotheLucasNumbers 79 13. TheLucasNumbers:FurtherPropertiesandExamples 100 14. Matrices,TheInverseTangentFunction,andanInfiniteSum 113 15. ThegcdPropertyfortheFibonacciNumbers 121 vii viii CONTENTS 16. AlternateFibonacciNumbers 126 17. OneFinalExample? 140 PARTTWO THECATALANNUMBERS 18. HistoricalBackground 147 19. AFirstExample:AFormulafortheCatalanNumbers 150 20. SomeFurtherInitialExamples 159 21. DyckPaths,Peaks,andValleys 169 22. YoungTableaux,Compositions,andVerticesandArcs 183 23. TriangulatingtheInteriorofaConvexPolygon 192 24. SomeExamplesfromGraphTheory 195 25. PartialOrders,TotalOrders,andTopologicalSorting 205 26. SequencesandaGeneratingTree 211 27. MaximalCliques,aComputerScienceExample,andtheTennisBall Problem 219 28. TheCatalanNumbersatSportingEvents 226 29. ARecurrenceRelationfortheCatalanNumbers 231 30. TriangulatingtheInteriorofaConvexPolygonfortheSecondTime 236 31. RootedOrderedBinaryTrees,PatternAvoidance,andData Structures 238 32. Staircases,ArrangementsofCoins,TheHandshakingProblem,and NoncrossingPartitions 250 33. TheNarayanaNumbers 268 34. RelatedNumberSequences:TheMotzkinNumbers, TheFineNumbers,andTheSchro¨derNumbers 282