%I A050930
%S A050930 1,1,6,20,69,196,554,1368,3240,7110,14896,29624,56755,104468,186484,
%T A050930 322800,544590,896259,1443834,2278640,3531647,5380064,8069672,11926928,
%U A050930 17392983,25042836,35637168,50152068,69853604,96344440,131669538
%N A050930 Number of directed multigraphs on 4 nodes with n arcs.
%F A050930 G.f.: (2*x^18 + 9*x^17 + 20*x^16 + 46*x^15 + 98*x^14 + 133*x^13 + 196*x^12 
               + 226*x^11 + 254*x^10 + 240*x^9 + 207*x^8 + 128*x^7 + 92*x^6 + 43*x^5 
               + 24*x^4 + 8*x^3 + 2*x^2-x + 1)/((x^4-1)^3*(x^3-1)^4*(x^2-1)^3*(x-1)^2).
%Y A050930 Cf. A037240.
%Y A050930 Sequence in context: A018808 A027107 A096487 this_sequence A074353 A075055 
               A146891
%Y A050930 Adjacent sequences: A050927 A050928 A050929 this_sequence A050931 A050932 
               A050933
%K A050930 easy,nonn
%O A050930 0,3
%A A050930 Vladeta Jovovic (vladeta(AT)eunet.rs), Dec 30 1999