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 A123550 Triangle read by rows: T(n,k) = number of unlabeled connected bicolored graphs having 2n nodes and k edges, which are invariant when the two color classes are interchanged. Here n >= 0, 0 <= k <= n^2. 2

%I

%S 0,1,0,0,0,1,1,0,0,0,0,0,2,2,1,1,1,0,0,0,0,0,0,0,4,6,6,6,5,4,2,1,1,1,

%T 0,0,0,0,0,0,0,0,0,9,15,23,31,36,34,31,27,21,14,9,6,4,2,1,1,1,0,0,0,0,

%U 0,0,0,0,0,0,0,20,44,84,134,196,249,288,313,317,303,267,224,180

%N Triangle read by rows: T(n,k) = number of unlabeled connected bicolored graphs having 2n nodes and k edges, which are invariant when the two color classes are interchanged. Here n >= 0, 0 <= k <= n^2.

%D R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1978.

%H R. W. Robinson, <a href="/A123550/b123550.txt">Rows 0 through 7, flattened</a>

%e Triangle begins:

%e n = 1

%e k = 0 : 0

%e k = 1 : 1

%e Total = 1

%e n = 2

%e k = 0 : 0

%e k = 1 : 0

%e k = 2 : 0

%e k = 3 : 1

%e k = 4 : 1

%e Total = 2

%e n = 3

%e k = 0 : 0

%e k = 1 : 0

%e k = 2 : 0

%e k = 3 : 0

%e k = 4 : 0

%e k = 5 : 2

%e k = 6 : 2

%e k = 7 : 1

%e k = 8 : 1

%e k = 9 : 1

%e Total = 7

%K nonn,tabf

%O 1,13

%A _N. J. A. Sloane_, Nov 14 2006

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Last modified April 1 16:25 EDT 2023. Contains 361695 sequences. (Running on oeis4.)