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!)
A245066 Central terms of triangles A001497 and A001498. 3
1, 3, 45, 1260, 51975, 2837835, 192972780, 15713497800, 1490818103775, 161505294575625, 19671344879311125, 2660996470946814000, 395823225053338582500, 64214706279807005422500, 11283441246308945238525000, 2134827083801652439128930000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..250

FORMULA

a(n) = A001497(2*n,n) = A001498(2*n,n).

O.g.f. A(x) satisfies 0 = 6*A(x) + (-2 + 54*x) * A'(x) + 27*x^2 * A''(x). - Michael Somos, Jul 11 2014

E.g.f. A(x) satisfies 0 = 6*A(x) + (-2 + 54*x) * A'(x) + (-2*x + 27*x^2) * A''(x). - Michael Somos, Jul 11 2014

a(n) = (3*n)! / (2^n * n!^2). - Michael Somos, Jul 11 2014

a(n) = (2*n-1)!! * [x^(2*n)] x^n/(1 - x)^(2*n+1). - Ilya Gutkovskiy, Nov 24 2017

EXAMPLE

G.f. = 1 + 3*x + 45*x^2 + 1260*x^3 + 51975*x^4 + 2837835*x^5 + ...

PROG

(Haskell)

a245066 n = a001497 (2 * n) n

(PARI) {a(n) = if( n<0, 0, (3*n)! / (2^n * n!^2))}; /* Michael Somos, Jul 11 2014 */

CROSSREFS

Sequence in context: A302106 A241242 A009088 * A187662 A113065 A144949

Adjacent sequences:  A245063 A245064 A245065 * A245067 A245068 A245069

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jul 11 2014

STATUS

approved

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 October 26 08:00 EDT 2021. Contains 348267 sequences. (Running on oeis4.)