login
A049387
Number of rooted unlabeled strongly connected digraphs with n nodes.
3
1, 1, 10, 287, 24427, 6222400, 4924590115, 12632686344657, 109225745061589342, 3281390460782419035867, 350135321051253376431022071, 134810599506208376766503740475912, 189491014587142646710566991248361106383, 981059614010249061197621212287544752507380541
OFFSET
1,3
COMMENTS
There is a rather difficult formula (simplified in 1973). The subsequent published value 6222928 for n=6 needs to be verified.
The correct value is 6222400. Terms up to a(7) have been confirmed by brute force using digraphs generated by nauty. - Andrew Howroyd, Jan 12 2022
LINKS
V. A. Liskovets, The number of strongly connected directed graphs, Mat. Notes, 8 (1970), 877-882
PROG
(PARI) \\ See PARI link in A350794 for program code.
A049387seq(15) \\ Andrew Howroyd, Jan 22 2022
CROSSREFS
Sequence in context: A077281 A239774 A360341 * A222672 A024295 A291658
KEYWORD
nonn
EXTENSIONS
Terms a(6) and beyond from Andrew Howroyd, Jan 12 2022
STATUS
approved