login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A025245 a(n) = (1/2)*s(n+3), where s = A025244. 0
1, 2, 5, 11, 26, 65, 163, 416, 1081, 2837, 7516, 20089, 54077, 146478, 398997, 1092215, 3003014, 8289569, 22964919, 63828252, 177931665, 497367721, 1393768952, 3914793457, 11019379609, 31079140922, 87818240869, 248571086403, 704722488690 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..29.

Paul Barry, On a Generalization of the Narayana Triangle, J. Int. Seq. 14 (2011) # 11.4.5.

FORMULA

G.f.: (1-x-x^2-4*x^3-sqrt(1-2*x-x^2-6*x^3+x^4))/(4*x^3). - Michael Somos, Jun 08 2000

Conjecture: (n+3)*a(n) +(-2*n-3)*a(n-1) -n*a(n-2) +3*(-2*n+3)*a(n-3) +(n-3)*a(n-4)=0. - R. J. Mathar, Feb 25 2015

PROG

(PARI) a(n)=polcoeff((-sqrt(1-2*x-x^2-6*x^3+x^4+x^4*O(x^n)))/4, n+3)

CROSSREFS

Sequence in context: A306563 A308060 A235496 * A300125 A307576 A079223

Adjacent sequences: A025242 A025243 A025244 * A025246 A025247 A025248

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 5 15:27 EST 2022. Contains 358588 sequences. (Running on oeis4.)