LinearAlgebraanditsApplications329(2001)49–59 www.elsevier.com/locate/laa StirlingmatrixviaPascalmatrix Gi-SangCheon a,∗,Jin-SooKim b aDepartmentofMathematics,DaejinUniversity,Pocheon487-711,SouthKorea bDepartmentofMathematics,SungkyunkwanUniversity,Suwon440-746,SouthKorea Received11May2000;accepted17November2000 SubmittedbyR.A.Brualdi Abstract ThePascal-typematricesobtainedfromtheStirlingnumbersofthefirstkinds(n,k)and ofthesecondkindS(n,k)arestudied,respectively.Itisshownthatthesematricescanbe factorizedbythePascalmatrices.AlsotheLDU-factorizationofaVandermondematrixof theformVn(x,x+1,...,x+n−1)foranyrealnumberxisobtained.Furthermore,some well-knowncombinatorialidentitiesareobtainedfromthematrixrepresentationoftheStirling numbers,andthesematricesaregeneralizedinoneortwovariables.©2001ElsevierScience Inc.Allrightsreserved. AMSclassification:05A19;05A10 Keywords:Pascalmatrix;Stirlingnumber;Stirlingmatrix 1.Introduction Forintegersnandkwithnk0,theStirlingnumbersofthefirstkinds(n,k) andofthesecondkindS(n,k)canbedefinedasthecoefficientsinthefollowing expansionofavariablex(see[3,pp.271–279]): n n−k k [x]n = (−1) s(n,k)x k=0 and ∗ Correspondingauthor. E-mailaddresses:
[email protected](G.-S.Cheon),
[email protected](J.-S.Kim). 0024-3795/01/$-seefrontmatter2001ElsevierScienceInc.Allrightsreserved. PII:S0024-3795(01)00234-8 50 G.-S. Cheon, J.-S. Kim / Linear Algebra and its Applications 329 (2001) 49–59 n n x = S(n,k)[x]k, (1.1) k=0 where x(x − 1) ···(x − n + 1) if n 1, [x] = (1.2) n 1ifn = 0. It is known that for an n, k 0, the s(n,k), S(n,k) and [n]k satisfy the following Pascal-type recurrence relations: s(n,k) = s(n − 1,k− 1) + (n − 1)s(n − 1,k), S(n,k) = S(n − 1,k− 1) + kS(n − 1,k), (1.3) [n]k =[n − 1]k + k[n − 1]k−1, where s(n,0) = s(0,k)= S(n,0) = S(0,k)=[0]k = 0ands(0, 0) = S(0, 0) = 1, and moreover the S(n,k) satisfies the following formula known as ‘vertical’ recur- rence relation: n− 1 n − 1 S(n,k) = S(l,k − 1).