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A307155
Number of connected, loopless 2-regular digraphs, no multiedges, on n nodes.
1
1, 0, 0, 1, 2, 5, 22, 90, 616, 4988, 46883, 493406, 5712809, 71909602
OFFSET
0,5
COMMENTS
Inverse Euler transform of A219889.
The Multiset Transform (number of loopless 2-regular digraphs on n nodes with c weakly connected components) of this sequence starts
in row 3 as:
1 ;
2 ;
5 ;
22 , 1 ;
90 , 2 ;
616 , 8 ;
4988 , 32 , 1 ;
46883 , 149 , 2 ;
493406 , 906 , 8 ;
5712809 , 6923 , 36 , 1 ;
71909602 , 61919 , 164 , 2 ;
CROSSREFS
Cf. A219889 (not necessarily connected), A005642 (loops admitted).
Sequence in context: A083465 A339646 A215100 * A144934 A346628 A371609
KEYWORD
nonn
AUTHOR
R. J. Mathar, Mar 27 2019
STATUS
approved