|
%I #6 Mar 27 2019 11:14:18
%S 1,0,0,1,2,5,22,90,616,4988,46883,493406,5712809,71909602
%N Number of connected, loopless 2-regular digraphs, no multiedges, on n nodes.
%C Inverse Euler transform of A219889.
%C The Multiset Transform (number of loopless 2-regular digraphs on n nodes with c weakly connected components) of this sequence starts
%C in row 3 as:
%C 1 ;
%C 2 ;
%C 5 ;
%C 22 , 1 ;
%C 90 , 2 ;
%C 616 , 8 ;
%C 4988 , 32 , 1 ;
%C 46883 , 149 , 2 ;
%C 493406 , 906 , 8 ;
%C 5712809 , 6923 , 36 , 1 ;
%C 71909602 , 61919 , 164 , 2 ;
%Y Cf. A219889 (not necessarily connected), A005642 (loops admitted).
%K nonn
%O 0,5
%A _R. J. Mathar_, Mar 27 2019
|
