OFFSET
1,2
FORMULA
a(n) = y(n,n), where y(m+1,n)=n*y(m,n)-y(m-1,n), with y(0,n)=y(1,n)=y(2,n)=1 for all n. - Benedict W. J. Irwin, Nov 03 2016
a(n) ~ exp(1) * n^(n-1). - Vaclav Kotesovec, Nov 05 2016
MATHEMATICA
Table[DifferenceRoot[Function[{y, m}, {y[1 + m] == n*y[m] - y[m - 1], y[0] == 1, y[1] == 1, y[2] == 1}]][n], {n, 2, 20}] (* Benedict W. J. Irwin, Nov 03 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ralf Stephan, May 31 2004
STATUS
approved