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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A107716 Inverse INVERT transform of triple factorial numbers (3*n-2)!!! (A007559). 7
1, 3, 21, 219, 2973, 49323, 964173, 21680571, 551173053, 15633866379, 489583062381, 16780438408539, 624935780160285, 25131869565110571, 1085528359404039117, 50124679063548821499, 2464153823558024331645, 128500643820213560377803, 7085182933810282490250285 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Column 0 of triangle A107717.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..380

FORMULA

G.f.: A(x) = 1 - 1/[1 + Sum_{n>=1} (3*n-2)!!! * x^n ] where (3*n-2)!!! = Product_{k=0..n-1} (3*k+1).

a(n) = Sum_{k, 0<=k<=n} A089949(n, k)*3^k . - Philippe Deléham, Aug 15 2005

G.f.: (1 - Q(0))/x where Q(k) = 1 - x*(3*k+1)/(1 - x*(3*k+3)/Q(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Mar 20 2013

G.f.: 1/x - 2 - 2/x/G(0), where G(k)= 1 + 1/(1 - x*(3*k+3)/(x*(3*k+4) + 1/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, May 25 2013

From Peter Bala, May 23 2017: (Start)

G.f. A(x) = 1/(1 + x - 4*x/(1 + 4*x - 7*x/(1 + 7*x - 10*x/(1 + 10*x - ...)))).

A(x) = 1/(1 + x - 4*x/(1 - 3*x/(1 - 7*x/(1 - 6*x/(1 - 10*x/(1 - 9*x - ...)))))). (End)

EXAMPLE

The triple factorials begin: {1,4,28,280,3640,58240,...}; thus the inverse INVERT transform of the triple factorials can be calculated by the g.f.s:

1/(1 + x + 4*x^2 + 28*x^3 + 280*x^4 + 3640*x^5 + 58240*x^6 +...) = (1 - x - 3*x^2 - 21*x^3 - 219*x^4 - 2973*x^5 - 49323*x^6 -...).

MAPLE

b:= proc(n) b(n):=  `if`(n=0, 1, b(n-1)*(3*n+1)) end:

a:= proc(n) a(n):= -`if`(n<0, 1, add(a(n-i-1)*b(i), i=0..n)) end:

seq(a(n), n=0..20);  # Alois P. Heinz, May 23 2017

PROG

(PARI) a(n)=polcoeff(1-(1+sum(k=1, n+1, prod(j=0, k-1, 3*j+1)*x^k)+x^2*O(x^n))^-1, n+1)

CROSSREFS

Cf. A007559, A000698, A107717.

Sequence in context: A168479 A158838 A236963 * A032033 A218494 A099121

Adjacent sequences:  A107713 A107714 A107715 * A107717 A107718 A107719

KEYWORD

nonn,easy

AUTHOR

Paul D. Hanna, May 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 12 12:43 EST 2018. Contains 317109 sequences. (Running on oeis4.)