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Triangle read by rows: chromatic invariant T(n,m) of the complete bipartite graph K_{m,n}.
0

%I #12 Aug 03 2021 01:55:07

%S 1,0,1,0,1,5,0,1,13,73,0,1,29,301,2069,0,1,61,1081,11581,95401,0,1,

%T 125,3613,57749,673261,6487445,0,1,253,11593,268381,4306681,55213453,

%U 610093513,0,1,509,36301,1191989,25794781,431525429,6077248381,75796724309,0,1,1021,111961,5136061,147587401,3173843821,56153444761,864806272861,12020754177001

%N Triangle read by rows: chromatic invariant T(n,m) of the complete bipartite graph K_{m,n}.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ChromaticInvariant.html">Chromatic Invariant</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CompleteBipartiteGraph.html">Complete Bipartite Graph</a>

%F T(m,n) = Sum_{k = 0..m-1} k!*(-1)^(k + m)*(k + 1)^n*Stirling2(m, k + 2) for max(m,n) > 1.

%e Triangle begins:

%e 1

%e 0 1

%e 0 1 5

%e 0 1 13 73

%e 0 1 29 301 2069

%t Join[{1}, Table[Sum[k! (-1)^(k + m) (k + 1)^n StirlingS2[m, k + 2], {k, 0, m - 1}], {n, 2, 10}, {m, n}]] // Flatten

%Y Main diagonal gives A048144.

%K nonn,tabl

%O 1,6

%A _Eric W. Weisstein_, Aug 31 2017