The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A064633 a(n) = 3^n*n!*(n+2)!/2!. 1
 1, 9, 216, 9720, 699840, 73483200, 10581580800, 1999918771200, 479980505088000, 142554210011136000, 51319515604008960000, 22016072194119843840000, 11096100385836401295360000, 6491218725714294757785600000, 4362098983680006077231923200000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Harry J. Smith, Table of n, a(n) for n = 0..75 FORMULA Hypergeometric g.f.: (1-3*x)^(-3). a(0)=1, a(n) = n!*subs(x=0, (d^n/dx^n)(-1/((3*x-1)^3))), n = 1, 2, ... From Amiram Eldar, Sep 27 2022: (Start) Sum_{n>=0} 1/a(n) = 6*BesselI(2,2/sqrt(3)). Sum_{n>=0} (-1)^n/a(n) = 6*BesselJ(2,2/sqrt(3)). (End) MATHEMATICA Table[3^n n! (n+2)!/2, {n, 0, 20}] (* Harvey P. Dale, Feb 25 2015 *) PROG (PARI) { for (n=0, 75, write("b064633.txt", n, " ", 3^n*n!*(n + 2)!/2) ) } \\ Harry J. Smith, Sep 20 2009 CROSSREFS Cf. A000244, A010791. Sequence in context: A007108 A007107 A217042 * A084942 A061718 A085741 Adjacent sequences: A064630 A064631 A064632 * A064634 A064635 A064636 KEYWORD nonn AUTHOR Karol A. Penson, Oct 01 2001 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 9 23:05 EST 2022. Contains 358710 sequences. (Running on oeis4.)