login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A182555 G.f.: (3-4*x-sqrt(1-4*x^2))/(2*(1-2*x)^2). 0
1, 2, 5, 12, 29, 68, 158, 360, 813, 1812, 4010, 8792, 19170, 41512, 89500, 191952, 410237, 873140, 1853042, 3919608, 8271126, 17406072, 36556580, 76602032, 160240594, 334554248, 697462628, 1451633520, 3017426468, 6263171792, 12985655736, 26889935776, 55626815005, 114947516916, 237318165314, 489482593592, 1008787357902, 2077219057240, 4274204436052 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..38.

F. Disanto and S. Rinaldi, Symmetric convex permutominoes and involutions, PU. M. A., Vol. 22 (2011), No. 1, pp. 39-60; See M_n.

FORMULA

Conjecture: n*(n-4)*a(n) +2*(5+2n-n^2)*a(n-1) -4*(n-2)*(n-5)*a(n-2) +8*(n-2)*(n-3)*a(n-3)=0. - R. J. Mathar, Jun 28 2012

a(n) ~ n*2^(n-1) * (1-2*sqrt(2/Pi)/sqrt(n)). - Vaclav Kotesovec, Jun 29 2013

CROSSREFS

Sequence in context: A266465 A079864 A131045 * A026721 A094975 A067687

Adjacent sequences:  A182552 A182553 A182554 * A182556 A182557 A182558

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, May 05 2012

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 19 17:48 EDT 2019. Contains 323395 sequences. (Running on oeis4.)