OFFSET
0,3
COMMENTS
a(n) is a specific instance of sequences having the form a(0)= x, a(n) = a*n*a(n-1)+k. (Here x =1, a = 2, and k =- 1). Sequences of this form have a closed form of n!*a^n*x + k*sum(n!*a^(n-j)/j!, j = 1..n). -Gary Detlefs, Mar 26 2018
FORMULA
a(n) = ceiling(2^n * n! * (2-sqrt(e))) = ceiling(A000165(n) * (2-sqrt(e))). - Gary Detlefs, Jul 18 2010
EXAMPLE
a(3) = 2*3*a(2) - 1 = 6*3 - 1 = 17.
MATHEMATICA
s=-1; lst={Abs[s]}; Do[s+=s++n; AppendTo[lst, Abs[s]], {n, 1, 5!, 2}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 23 2008 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Henry Bottomley, Jun 19 2000
EXTENSIONS
More terms from James A. Sellers, Jul 04 2000
STATUS
approved