%I A001373 M1597 N0623
%S A001373 1,0,1,2,6,13,40,100,291,797,2273,6389,18264,51916,148666,425529,
%T A001373 1221900,3511507,10111043,29142941,84112009,243000149,702758065,
%U A001373 2034150215,5892907566,17084615940,49567063847,143902155133
%N A001373 Functional digraphs (digraphs of functions on n nodes where every node 
               has outdegree 1 and loops of length 1 are forbidden).
%D A001373 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A001373 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001373 F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 
               1973, p. 70, Table 3.4.1.
%D A001373 R. C. Read, Note on number of functional digraphs, Math. Ann., vol. 143 
               (1961), pp. 109-111.
%H A001373 N. J. A. Sloane, <a href="transforms.txt">Transforms</a>
%H A001373 L. Travis, <a href="http://arXiv.org/abs/math.CO/9811127">[math/9811127] 
               Graphical Enumeration: A Species-Theoretic Approach</a>
%Y A001373 Euler transform of A002862. Cf. A001372.
%Y A001373 Sequence in context: A026550 A124124 A052450 this_sequence A057243 A012470 
               A056592
%Y A001373 Adjacent sequences: A001370 A001371 A001372 this_sequence A001374 A001375 
               A001376
%K A001373 nonn,nice,easy
%O A001373 0,4
%A A001373 N. J. A. Sloane (njas(AT)research.att.com).
%E A001373 Sequence extended by Paul Zimmermann; more terms and better description 
               from Christian Bower.