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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A081922 Expansion of exp(4x)/sqrt(1-x^2). 1
1, 4, 17, 76, 361, 1844, 10321, 64348, 453329, 3619684, 32666161, 329434604, 3677682937, 44901581716, 595567550321, 8505627039484, 130307878338721, 2126927187154628, 36912563369550289, 677277819029706124 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Binomial transform of A081921

Generally, if e.g.f. = exp(p*x)/sqrt(1-x^2), then a(n) ~ n^n * (exp(p)+(-1)^n*exp(-p)) / exp(n). - Vaclav Kotesovec, Feb 04 2014

LINKS

Table of n, a(n) for n=0..19.

FORMULA

E.g.f. exp(4x)/sqrt(1-x^2).

Conjecture: -a(n) +4*a(n-1) +(n-1)^2*a(n-2) -4*(n-1)*(n-2)*a(n-3)=0. - R. J. Mathar, Nov 09 2012

a(n) ~ n^n * (exp(4)+(-1)^n*exp(-4)) / exp(n). - Vaclav Kotesovec, Feb 04 2014

MATHEMATICA

With[{nn=20}, CoefficientList[Series[Exp[4x]/Sqrt[1-x^2] , {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, May 07 2012 *)

CROSSREFS

Cf. A081919, A081920, A081921.

Sequence in context: A239204 A005572 A202879 * A124325 A151248 A104455

Adjacent sequences:  A081919 A081920 A081921 * A081923 A081924 A081925

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Apr 01 2003

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 November 16 02:33 EST 2018. Contains 317252 sequences. (Running on oeis4.)