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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A190864 Expansion of 1/(1-x*sqrt(1+4*x^2)). 1
1, 1, 1, 3, 5, 5, 9, 21, 29, 31, 65, 143, 181, 183, 441, 1019, 1165, 893, 2929, 7829, 7589, 1677, 19305, 66585, 49661, -44279, 126881, 638085, 325525, -1024831, 833049, 6876389, 2135149, -16612625, 5467345, 81608271, 14007941, -244131809, 35877321 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..100

FORMULA

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

MATHEMATICA

CoefficientList[Series[1/(1-x Sqrt[1+4x^2]), {x, 0, 40}], x] (* Harvey P. Dale, Mar 04 2015 *)

PROG

(PARI) x='x+O('x^66); /* that many terms */

Vec(1/(1-x*sqrt(1+4*x^2))) /* show terms */ /* Joerg Arndt, May 22 2011 */

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

CROSSREFS

Sequence in context: A120841 A145282 A049757 * A155537 A164663 A098971

Adjacent sequences:  A190861 A190862 A190863 * A190865 A190866 A190867

KEYWORD

sign

AUTHOR

Vladimir Kruchinin, May 21 2011

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 October 16 17:49 EDT 2019. Contains 328102 sequences. (Running on oeis4.)