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A350749
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Triangle read by rows: T(n,k) is the number of oriented graphs on n labeled nodes with k arcs, n >= 0, k = 0..n*(n-1)/2.
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1
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1, 1, 1, 2, 1, 6, 12, 8, 1, 12, 60, 160, 240, 192, 64, 1, 20, 180, 960, 3360, 8064, 13440, 15360, 11520, 5120, 1024, 1, 30, 420, 3640, 21840, 96096, 320320, 823680, 1647360, 2562560, 3075072, 2795520, 1863680, 860160, 245760, 32768
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OFFSET
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0,4
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LINKS
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FORMULA
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T(n,k) = 2^k * binomial(n*(n-1)/2, k) = A013609(n*(n-1)/2, k).
T(n,k) = [y^k] (1+2*y)^(n*(n-1)/2).
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EXAMPLE
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Triangle begins:
[0] 1;
[1] 1;
[2] 1, 2;
[3] 1, 6, 12, 8;
[4] 1, 12, 60, 160, 240, 192, 64;
[5] 1, 20, 180, 960, 3360, 8064, 13440, 15360, 11520, 5120, 1024;
...
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PROG
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(PARI) T(n, k) = 2^k * binomial(n*(n-1)/2, k)
(PARI)
row(n) = {Vecrev((1+2*y)^(n*(n-1)/2))}
{ for(n=0, 6, print(row(n))) }
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CROSSREFS
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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