OFFSET
2,2
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
E. Andresen, K. Kjeldsen, On certain subgraphs of a complete transitively directed graph, Discrete Math. 14 (1976), no. 2, 103-119.
FORMULA
a(n) = p(n-1)*Sum_{j=0..n-2} (-1)^j*(n-1-j)/p(j), where p(0)=1, p(k) = Product_{i=1..k} (2^i - 1) for k > 0. - Emeric Deutsch, Jan 23 2005
MAPLE
p:=proc(n) if n=0 then 1 else product(2^i-1, i=1..n) fi end: a:=n->p(n-1)*sum((-1)^j*(n-1-j)/p(j), j=0..n-2): seq(a(n), n=2..17); # Emeric Deutsch, Jan 23 2005
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Emeric Deutsch, Jan 23 2005
STATUS
approved