A098559 Expansion of e.g.f. (1+3*x)/(1-3*x).

1, 6, 36, 324, 3888, 58320, 1049760, 22044960, 529079040, 14285134080, 428554022400, 14142282739200, 509122178611200, 19855764965836800, 833942128565145600, 37527395785431552000, 1801314997700714496000, 91867064882736439296000, 4960821503667767721984000

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Formula

a(n) = 6 * A034001(n) for n >= 1.

a(n) = 2*3^n*n! - 0^n.

Sum_{n>=0} 1/a(n) = (exp(1/3)+1)/2. - Amiram Eldar, Feb 02 2023

Mathematica

Join[{1}, Table[2*3^n n!, {n, 20}]] (* Harvey P. Dale, Aug 08 2014 *)

Prog

(Magma) [2*3^n*Factorial(n)-0^n: n in [0..20]]; // Vincenzo Librandi, Aug 08 2014

Crossrefs

Cf. A098558, A032184.

Sequence in context: A064239 A047898 A337042 * A129584 A052559 A367490

Adjacent sequences: A098556 A098557 A098558 * A098560 A098561 A098562

Keyword

easy,nonn

Author

Paul Barry, Sep 14 2004

Status

approved