A066118 a(n) = n!*(3*n-1)/2.

1, 5, 24, 132, 840, 6120, 50400, 463680, 4717440, 52617600, 638668800, 8382528000, 118313395200, 1787154969600, 28768836096000, 491685562368000, 8892185702400000, 169662903201792000, 3406062811447296000, 71770609241210880000, 1583819207322992640000

Offset: 1

Author

George E. Antoniou, Dec 05 2001

Keywords

• nonn
• easy

Links

• Harry J. Smith, Table of n, a(n) for n=1..100

Programs

Mathematica

Array[#!*(3*#-1)/2 &, 25] (* Paolo Xausa, Feb 16 2024 *)

PARI

{ for (n=1, 100, write("b066118.txt", n, " ", (n!*(3*n - 1))/2) ) } \\ Harry J. Smith, Feb 01 2010

Formula

E.g.f.: (1+x/2)/(1-x)^2. - Len Smiley, Dec 06 2001

3*a(n) +(-3*n-7)*a(n-1) +4*(n-1)*a(n-2)=0. - R. J. Mathar, Oct 30 2015

(-3*n+4)*a(n) +n*(3*n-1)*a(n-1)=0. - R. J. Mathar, Oct 30 2015

a(n) = A001563(n) + A001286(n). - Anton Zakharov, Oct 17 2016