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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A116396 Expansion of 2/((2+x)*sqrt(1-4*x)-x). 1
1, 2, 7, 25, 93, 353, 1358, 5273, 20614, 81003, 319584, 1264924, 5019743, 19963699, 79541181, 317406302, 1268283199, 5073605801, 20316709251, 81427911966, 326612013623, 1310968893954, 5265285993860, 21158914176719, 85071253608611 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Diagonal sums of number triangle A116395.

Diagonal sums of the Riordan matrix ((1-sqrt(1-4x))/(2x*sqrt(1-4x)),(1-sqrt(1-4x))/(2*sqrt(1-4x))) (A035324) [Emanuele Munarini, Apr 26 2011]

LINKS

Table of n, a(n) for n=0..24.

FORMULA

a(n)=sum{k=0..floor(n/2), (4^(n-k)/2^k)*sum{j=0..k, C(k,j)C(n-k+(j-1)/2,n-k)(-1)^(k-j)}}.

MATHEMATICA

CoefficientList[Series[(x+(2+x)Sqrt[1-4x])/(2-6x-8x^2-2x^3), {x, 0, 25}], x]) [Emanuele Munarini, Apr 26 2011]

CROSSREFS

Sequence in context: A270785 A199247 A242728 * A150453 A150454 A150455

Adjacent sequences:  A116393 A116394 A116395 * A116397 A116398 A116399

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Feb 12 2006

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 February 24 21:33 EST 2018. Contains 299628 sequences. (Running on oeis4.)