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Search: id:A126066
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| A126066 |
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Triangle read by rows: T(n,k)=of number of unlabeled digraphs on n nodes and k arcs up to reversing the arcs, k=0..n*(n-1). |
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1
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| 1, 1, 1, 1, 1, 1, 3, 3, 3, 1, 1, 1, 1, 4, 9, 18, 24, 30, 24, 18, 9, 4, 1, 1, 1, 1, 4, 11, 38, 89, 210, 382, 616, 787, 880, 787, 616, 382, 210, 89, 38, 11, 4, 1, 1, 1, 1, 4, 12, 48, 165, 567, 1703, 4623, 10836, 22273, 39866, 62650, 86209, 104456, 111256, 104456, 86209
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OFFSET
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1,7
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COMMENT
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Row sums give A054933.
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EXAMPLE
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1; 1,1,1; 1,1,3,3,3,1,1; 1,1,4,9,18,24,30,24,18,9,4,1,1; ... . G.f. for fourth row is obtained if we set x(i) = 1+x^i, i=1..12 in (1/48)*(x(1)^12+12*x(1)^2*x(2)^5+4*x(2)^6+8*x(3)^4+12*x(4)^3+3*x(1)^4*x(2)^4+8*x(6)^2)
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CROSSREFS
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Sequence in context: A086634 A066601 A110566 this_sequence A130974 A131289 A064353
Adjacent sequences: A126063 A126064 A126065 this_sequence A126067 A126068 A126069
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KEYWORD
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nonn,tabf
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Feb 28 2007
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