login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A086621 Main diagonal of square table A086620 of coefficients, T(n,k), of x^n*y^k in f(x,y) that satisfies f(x,y) = 1/(1-x-y) + xy*f(x,y)^2. 3

%I

%S 1,3,14,79,504,3514,26172,204831,1664696,13930840,119312544,

%T 1041227642,9228614836,82867255956,752405060536,6897376441167,

%U 63760133568096,593763928313128,5565678569009328,52475976165495960,497376657383374560,4736680863568248480,45304174896889357440

%N Main diagonal of square table A086620 of coefficients, T(n,k), of x^n*y^k in f(x,y) that satisfies f(x,y) = 1/(1-x-y) + xy*f(x,y)^2.

%H Andrew Howroyd, <a href="/A086621/b086621.txt">Table of n, a(n) for n = 0..500</a>

%F a(n) = Sum_{j=0..n} binomial(n,j) * binomial(2*n-j,n) * binomial(2*j,j)/(j+1). - _Andrew Howroyd_, Apr 11 2021

%o (PARI) a(n) = {sum(j=0, n, binomial(n,j)*binomial(2*n-j, n)*binomial(2*j, j)/(j+1))} \\ _Andrew Howroyd_, Apr 11 2021

%Y Cf. A086620 (table), A086622 (antidiagonal sums).

%K nonn

%O 0,2

%A _Paul D. Hanna_, Jul 24 2003

%E Terms a(18) and beyond from _Andrew Howroyd_, Apr 11 2021

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 10 04:49 EDT 2021. Contains 343748 sequences. (Running on oeis4.)