OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..450
FORMULA
a(n) ~ (exp(2) + (-1)^n) * n^(n-1) / exp(n). - Vaclav Kotesovec, Jun 22 2015
a(n) = ((2*n-3)*a(n-1) + (n-1)*(n^2-5*n+5)*a(n-2) + 2*(n-1)*(n-2)*(n-3)*(a(n-4)-a(n-3)))/(n-2) for n >= 4. - Alois P. Heinz, Jan 30 2020
MAPLE
a:= proc(n) option remember; `if`(n<4, [1$2, 2, 4][n+1],
((2*n-3)*a(n-1) +(n-1)*(n^2-5*n+5)*a(n-2)
+2*(n-1)*(n-2)*(n-3)*(a(n-4)-a(n-3)))/(n-2))
end:
seq(a(n), n=0..25); # Alois P. Heinz, Jun 22 2015
MATHEMATICA
CoefficientList[Series[E^(x-Sqrt[1-x^2]+1), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jun 22 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Karol A. Penson, Jun 22 2015
STATUS
approved