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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A001193 a(n) = (n+1)(2n)!/(2^n*n!) ( = (n+1)(2n-1)!!).
(Formerly M1944 N0770)
6
1, 2, 9, 60, 525, 5670, 72765, 1081080, 18243225, 344594250, 7202019825, 164991726900, 4111043861925, 110681950128750, 3201870700153125, 99044533658070000, 3262279327362680625, 113987877673731311250, 4211218814057295665625, 164015890652757831187500 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Solution to y'=A(x), y(0)=0 satisfies 0=x^2+2*y^2*x-y^2. - Michael Somos, Mar 11 2004

REFERENCES

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 167.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

T. D. Noe, Table of n, a(n) for n = 0..100

FORMULA

E.g.f.: (1-x)/(1-2x)^(3/2) = d/dx x/(1-2x)^(1/2).

a(n) = uppermost term in the vector (M(T))^n * [1,0,0,0,...] where T = Transpose, and M = the production matrix:

1, 2

1, 2, 3

1, 2, 3, 4

1, 2, 3, 4, 5

...

- Gary W. Adamson, Jul 08 2011

G.f.: A(x)=1 + 2*x/(G(0) -2*x) ; G(k) =1 + k + x*(k+2)*(2*k+1) - x*(k+1)*(k+3)*(2*k+3)/G(k+1); (continued fraction). - Sergei N. Gladkovskii, Dec 06 2011

G.f.: U(0)/2  where U(k)= 1 + (2*k+1)/(1 - x/(x + 1/U(k+1))) ; (continued fraction, 3-step). - Sergei N. Gladkovskii, Sep 25 2012

a(n) = (n + 1)*(2*n - 1)/n * a(n-1). a(n) = 2*a(n) + (2*n - 3)*(2*n + 1)*a(n-1). - Peter Bala, Nov 07 2016

MAPLE

restart: G(x):=(1-x)/(1-2*x)^(3/2): f[0]:=G(x): for n from 1 to 29 do f[n]:=diff(f[n-1], x) od:x:=0:seq(f[n], n=0..17); # Zerinvary Lajos, Apr 04 2009

MATHEMATICA

Table[(n+1) (2*n-1)!!, {n, 0, 20}] (* Vladimir Joseph Stephan Orlovsky, Apr 14 2011 *)

PROG

(PARI) a(n)=if(n<0, 0, (n+1)*(2*n)!/(2^n*n!))

CROSSREFS

From Johannes W. Meijer, Nov 12 2009: (Start)

Equals the first right hand column of A167591.

Equals the first left hand column of A167594.

(End)

Sequence in context: A120970 A111558 A168449 * A161391 A120014 A036774

Adjacent sequences:  A001190 A001191 A001192 * A001194 A001195 A001196

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

Better description from Wouter Meeussen, Mar 08 2001

More terms from James A. Sellers, May 01 2000

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 September 24 04:27 EDT 2017. Contains 292403 sequences.