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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A111962 Expansion of 1/(sqrt(1-2x-3x^2)-x^2). 1
1, 1, 4, 9, 27, 74, 215, 619, 1808, 5293, 15579, 45986, 136141, 403937, 1200854, 3575835, 10663105, 31836508, 95156251, 284684303, 852427700, 2554346249, 7659427811, 22981483554, 68992151795, 207223579671, 622697586944 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Diagonal sums of A111960.

LINKS

Table of n, a(n) for n=0..26.

FORMULA

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

CROSSREFS

Sequence in context: A214418 A164342 A034527 * A307528 A198095 A256096

Adjacent sequences:  A111959 A111960 A111961 * A111963 A111964 A111965

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Aug 23 2005

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 July 17 16:38 EDT 2019. Contains 325107 sequences. (Running on oeis4.)