%I A048144
%S A048144 1,1,5,73,2069,95401,6487445,610093513,75796724309,12020754177001,
%T A048144 2369364111428885,568128719132038153,162835627057766030549,54975855375379966645801,
%U A048144 21593185551426744571090325,9762238510837560633366673993,5033241437347149354018370856789
%N A048144 Sum_{k=0..n} (k!)^2*Stirling_2(n,k)^2.
%C A048144 Number of digraphs with loops, with labeled vertices and labeled arcs, 
               with n arcs and with no vertex of indegree 0 or outdegree 0, cf. 
               A121936, A122418, A122399. - Vladeta Jovovic (vladeta(AT)eunet.rs), 
               Sep 06 2006
%C A048144 Chromatic invariant of the complete bipartite graph K_{n-1,n-1}
%H A048144 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               ChromaticInvariant.html">Chromatic Invariant</a>
%F A048144 E.g.f.: Sum_{n>=0} Sum_{j=0..n} (-1)^(n-j)*binomial(n,j)*(exp(j*x)-1)^n. 
               a(n) = Sum_{k=0..n} Stirling2(n,k)*k!*A104602(k). - Vladeta Jovovic 
               (vladeta(AT)eunet.rs), Mar 25 2006
%Y A048144 Sequence in context: A005259 A062440 A126748 this_sequence A144682 A096987 
               A096538
%Y A048144 Adjacent sequences: A048141 A048142 A048143 this_sequence A048145 A048146 
               A048147
%K A048144 nonn,easy
%O A048144 0,3
%A A048144 N. J. A. Sloane (njas(AT)research.att.com).