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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A270709 a(n) = (n+1)*Sum_{k=0..(n-1)/2} (binomial(k+1,n-2*k-1)*binomial(2*k,k)/(k+1)^2). 2
0, 2, 3, 2, 5, 7, 14, 26, 51, 103, 209, 435, 910, 1930, 4122, 8874, 19227, 41893, 91751, 201839, 445841, 988403, 2198547, 4905147, 10974210, 24615134, 55341636, 124694354, 281525678, 636802626, 1442953404, 3274997130, 7444505615, 16946749249 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

FORMULA

G.f.: ((3*x+2)*(1-sqrt(1-4*(x^3+x^2))))/(2*(x^2+x)).

a(n) ~ (3*r+2) * sqrt(3-4*r^2) * 2^(2*n+2) * r^(n+3) * (r+1)^(n+1) / (n^(3/2) * sqrt(Pi)), where r = 0.41964337760708... is the real root of the equation 4*r^2*(1+r) = 1. - Vaclav Kotesovec, Mar 22 2016

MATHEMATICA

Table[(n+1)*Sum[Binomial[k+1, n-2*k-1] * Binomial[2*k, k] / (k+1)^2, {k, 0, (n-1)/2}], {n, 0, 20}] (* Vaclav Kotesovec, Mar 22 2016 *)

PROG

(Maxima)

makelist(coeff(taylor(((3*x+2)*(1-sqrt(1-4*(x^3+x^2))))/(2*(x^2+x)), x, 0, 15), x, n), n, 0, 15);

a(n):=(n+1)*sum((binomial(k+1, n-2*k-1)*binomial(2*k, k))/(k+1)^2, k, 0, (n-1)/2);

(PARI) x='x+O('x^200); concat(0, Vec(((3*x+2)*(1-sqrt(1-4*(x^3+x^2))))/(2*(x^2+x)))) \\ Altug Alkan, Mar 22 2016

CROSSREFS

Cf. A000108.

Sequence in context: A092550 A058977 A085818 * A064939 A248012 A151549

Adjacent sequences:  A270706 A270707 A270708 * A270710 A270711 A270712

KEYWORD

nonn

AUTHOR

Vladimir Kruchinin, Mar 22 2016

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 20 18:08 EDT 2018. Contains 316401 sequences. (Running on oeis4.)