OFFSET
0,3
LINKS
Robert Israel, Table of n, a(n) for n = 0..225
FORMULA
a(n) = Sum_{k=0..2n-1} (2n-1)!/k! - Sum_{k=0..n-1} (n-1)!/k! = A000522(2*n-1) - A000522(n-1). - Robert Israel, Nov 14 2017
MAPLE
a := n -> exp(1)*(GAMMA(2*n, 1) - GAMMA(n, 1)):
seq(simplify(a(n)), n=0..15);
# Alternative:
A000522:= gfun:-rectoproc({(-x-2)*d(1+x)+(x+4)*d(x+2)-d(x+3), d(0) = 1, d(1) = 2, d(2) = 5}, d(x), remember):
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Nov 14 2017
STATUS
approved