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A275421
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Triangle read by rows: T(n,k) = number of graphs with n edges and k connected components.
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13
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1, 1, 1, 3, 1, 1, 5, 4, 1, 1, 12, 8, 4, 1, 1, 30, 23, 9, 4, 1, 1, 79, 57, 26, 9, 4, 1, 1, 227, 160, 68, 27, 9, 4, 1, 1, 710, 456, 197, 71, 27, 9, 4, 1, 1, 2322, 1402, 567, 208, 72, 27, 9, 4, 1, 1, 8071, 4468, 1748, 604, 211, 72, 27, 9, 4, 1, 1, 29503, 15071, 5555, 1874
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,4
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COMMENTS
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Multiset transformation of A002905.
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LINKS
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Peter Steinbach, Field Guide to Simple Graphs, Volume 4, Table 1.1a, Part 1 (For Volumes 1, 2, 3, 4 of this book see A000088, A008406, A000055, A000664, respectively.)
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FORMULA
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T(n,k) = Sum_{c_i*N_i=n,i=1..k} binomial(T(N_i,1)+c_i-1,c_i) for 1<k<=n.
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EXAMPLE
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1
1 1
3 1 1
5 4 1 1
12 8 4 1 1
30 23 9 4 1 1
79 57 26 9 4 1 1
227 160 68 27 9 4 1 1
710 456 197 71 27 9 4 1 1
2322 1402 567 208 72 27 9 4 1 1
8071 4468 1748 604 211 72 27 9 4 1 1
29503 15071 5555 1874 615 212 72 27 9 4 1
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MATHEMATICA
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rows = 12;
A002905 = Import["https://oeis.org/A002905/b002905.txt", "Table"][[All, 2]];
gf = Product[(1 - y x^j)^-A002905[[j+1]], {j, 1, rows}];
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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