OFFSET
1,2
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..354
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 594.
Norihiro Nakashima and Shuhei Tsujie, Enumeration of Flats of the Extended Catalan and Shi Arrangements with Species, arXiv:1904.09748 [math.CO], 2019.
FORMULA
5*a(n) = (5*n)(!^5) = Product_{j=1..n} 5*j = 5^(n-1)*n!.
E.g.f.: (-1 + (1-5*x)^(-1))/5, a(0) = 0.
D-finite with recurrence: a(n) - 5*n*a(n-1) = 0. - R. J. Mathar, Feb 24 2020
From Amiram Eldar, Jan 08 2022: (Start)
Sum_{n>=1} 1/a(n) = 5*(exp(1/5)-1).
Sum_{n>=1} (-1)^(n+1)/a(n) = 5*(1-exp(-1/5)). (End)
MAPLE
seq(5^(n-1)*n!, n=1..20); # G. C. Greubel, Aug 23 2019
MATHEMATICA
Array[5^(# - 1) #! &, 16] (* Michael De Vlieger, May 30 2019 *)
PROG
(PARI) vector(20, n, 5^(n-1)*n!) \\ G. C. Greubel, Aug 23 2019
(Magma) [5^(n-1)*Factorial(n): n in [1..20]]; // G. C. Greubel, Aug 23 2019
(Sage) [5^(n-1)*factorial(n) for n in (1..20)] # G. C. Greubel, Aug 23 2019
(GAP) List([1..20], n-> 5^(n-1)*Factorial(n) ); # G. C. Greubel, Aug 23 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
STATUS
approved