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Search: id:A127538
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| A127538 |
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Triangle read by rows: T(n,k) is the number of ordered trees with n edges having k odd-length branches starting at the root (0<=k<=n). |
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+0
4
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| 1, 0, 1, 1, 0, 1, 0, 4, 0, 1, 3, 3, 7, 0, 1, 3, 22, 6, 10, 0, 1, 16, 43, 50, 9, 13, 0, 1, 37, 175, 101, 87, 12, 16, 0, 1, 134, 503, 448, 177, 133, 15, 19, 0, 1, 411, 1784, 1305, 862, 271, 188, 18, 22, 0, 1, 1411, 5887, 4848, 2524, 1444, 383, 252, 21, 25, 0, 1, 4747, 20604
(list; table; graph; listen)
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OFFSET
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0,8
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COMMENT
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Row sums are the Catalan numbers (A000108). T(n,0)=A127539(n). Sum(k*T(n,k),k=0..n)=A127540(n).
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FORMULA
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G.f.=(1+z)/(1+z-z^2*C-tzC), where C =[1-sqrt(1-4z)]/(2z) is the Catalan function.
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EXAMPLE
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T(2,2)=1 because we have the tree /\.
Triangle starts:
1;
0,1;
1,0,1;
0,4,0,1;
3,3,7,0,1;
3,22,6,10,0,1;
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MAPLE
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C:=(1-sqrt(1-4*z))/2/z: G:=(1+z)/(1+z-z^2*C-t*z*C): Gser:=simplify(series(G, z=0, 15)): for n from 0 to 12 do P[n]:=sort(coeff(Gser, z, n)) od: for n from 0 to 12 do seq(coeff(P[n], t, j), j=0..n) od; # yields sequence in triangular form
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CROSSREFS
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Cf. A000108, A127539, A127540, A127541.
Sequence in context: A141277 A096793 A155998 this_sequence A096008 A122873 A115715
Adjacent sequences: A127535 A127536 A127537 this_sequence A127539 A127540 A127541
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KEYWORD
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nonn,tabl
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 01 2007
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