%I A005641 M2757
%S A005641 1,3,8,27,131,711,5055,41607,389759,4065605,46612528,581713045,
%T A005641 7846380548,113718755478,1762208816647,29073392136390,508777045979418
%N A005641 Number of 2-diregular digraphs with n nodes.
%D A005641 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005641 M. V. S. Ramanath; T. R. Walsh, Enumeration and generation of a class 
               of regular digraphs, J. Graph Theory 11 (1987), no. 4, 471-479.
%Y A005641 Sequence in context: A104854 A030495 A074271 this_sequence A148845 A148846 
               A163062
%Y A005641 Adjacent sequences: A005638 A005639 A005640 this_sequence A005642 A005643 
               A005644
%K A005641 nonn
%O A005641 2,2
%A A005641 N. J. A. Sloane (njas(AT)research.att.com).