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!)
A258392 Number of 2n-length strings of balanced parentheses of exactly 4 different types that are introduced in ascending order. 2
14, 420, 8580, 150150, 2432430, 37777740, 572827580, 8568059500, 127199546012, 1881416537000, 27792098497800, 410634370077750, 6074408847920670, 90017212151219100, 1336818529866319500, 19898794932394570500, 296909055625560798420, 4440849374395184751000 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 4..800

FORMULA

Recurrence: (n-2)*(n-1)*n*(n+1)*a(n) = 20*(n-2)*(n-1)*n*(2*n - 1)*a(n-1) - 140*(n-2)*(n-1)*(2*n - 3)*(2*n - 1)*a(n-2) + 400*(n-2)*(2*n - 5)*(2*n - 3)*(2*n - 1)*a(n-3) - 384*(2*n - 7)*(2*n - 5)*(2*n - 3)*(2*n - 1)*a(n-4). - Vaclav Kotesovec, Jun 01 2015

a(n) ~ 16^n / (24*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jun 01 2015

CROSSREFS

Column k=4 of A253180.

Sequence in context: A239785 A275025 A236156 * A269504 A033815 A187358

Adjacent sequences:  A258389 A258390 A258391 * A258393 A258394 A258395

KEYWORD

nonn

AUTHOR

Alois P. Heinz, May 28 2015

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 May 9 20:41 EDT 2021. Contains 343746 sequences. (Running on oeis4.)