OFFSET
1,3
COMMENTS
Equivalently a(n) is the number of labeled digraphs on [n] with no out-nodes. Cf. A362013. - Geoffrey Critzer, Apr 13 2023
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..50
FORMULA
a(n) = (2^(n-1)-1)^n = Sum_{k=0..n} (-1)^k*binomial(n, k)*2^((n-k)*(n-1)).
a(n) = A092477(n, n-1).
Sum_{n>=0} a(n)*x^n/A011266(n) = (Sum_{n>=0} (-x)^n/A011266(n))*(Sum_{n>=0} 2^(n(n-1))*x^n/A011266(n)). - Geoffrey Critzer, Apr 13 2023
PROG
(PARI) a(n) = {(2^(n-1)-1)^n} \\ Andrew Howroyd, Jan 05 2020
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Vladeta Jovovic, Aug 27 2003
EXTENSIONS
Terms a(11) and beyond from Andrew Howroyd, Jan 05 2020
STATUS
approved