This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A069640 Let M_n be the n X n matrix with M_n(i,j)=1/(i+j+1); then a(n)=1/det(M_n). 3

%I

%S 3,240,378000,10668672000,5175372787200000,42202225467872870400000,

%T 5708700736339601341845504000000,

%U 12701009683686045652926579789004800000000,462068939479146913162956288390362787269836800000000

%N Let M_n be the n X n matrix with M_n(i,j)=1/(i+j+1); then a(n)=1/det(M_n).

%D Wolfram Research, 1991 Mathematica Conference, Elementary Tutorial Notes, Section 1, Introduction to Mathematica, Paul Abbott, page 19.

%H Robert Israel, <a href="/A069640/b069640.txt">Table of n, a(n) for n = 1..40</a>

%F a(n) = (2*n+1)!!*(n!*Product[(2*k)!/k!/(k+1)!,{k,0,n}])^2. a(n) = (2*n+1)!!*(n!*A003046(n))^2, where A003046(n)is the Product of first n Catalan numbers A000108(n). a(n) = (2*n+1)!*n!/(2^n)*A003046(n)^2. - _Alexander Adamchuk_, May 17 2006

%F a(n) ~ A^3 * 2^(2*n^2+3*n+11/12) / (exp(1/4) * n^(7/4) * Pi^(n+1)), where A = 1.2824271291... is the Glaisher-Kinkelin constant (see A074962). - _Vaclav Kotesovec_, Nov 13 2014

%p seq(1/LinearAlgebra:-Determinant(LinearAlgebra:-HilbertMatrix(n,n,-1)),n=1..10); # _Robert Israel_, Sep 26 2018

%t Hilbert[n_Integer] := Table[1/(i + j + 1), {i, n}, {j, n}]; Table[ 1 / Det[ Hilbert[n]], {n, 1, 8}] (* _Robert G. Wilson v_, Mar 13 2004 *)

%t Table[(2*n+1)!!*(n!*Product[(2*k)!/k!/(k+1)!,{k,0,n}])^2,{n,1,11}] (* _Alexander Adamchuk_, May 17 2006 *)

%t Table[2^(2*n^2+2*n-1/12) * Glaisher^3 * BarnesG[n+3/2]^2 *(n!)^2 *(2*n+1)!!/(E^(1/4)*Pi^(n+1/2)*BarnesG[n+3]^2), {n, 1, 11}] (* _Vaclav Kotesovec_, Mar 09 2014 *)

%o (PARI) for(n=1,10,print1(1/matdet(matrix(n,n,i,j,1/(i+j+1))),","))

%Y Cf. A000108, A003046, A005249, A067689, A074962.

%K easy,nonn

%O 1,1

%A _Benoit Cloitre_, Apr 21 2002

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 21 08:27 EDT 2018. Contains 316405 sequences. (Running on oeis4.)