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A210664
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Square array read by upwards antidiagonals: T(m,n) is the number of simple 3-connected triangulations of a closed region in the plane with m+3 given external edges and 3n+m internal edges, m>=0, n>=1.
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8
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1, 1, 0, 1, 2, 1, 1, 5, 6, 3, 1, 9, 20, 22, 12, 1, 14, 50, 85, 91, 52, 1, 20, 105, 254, 385, 408, 241, 1, 27, 196, 644, 1287, 1836, 1938, 1173, 1, 35, 336, 1448, 3696, 6630, 9120, 9614, 5929, 1, 44, 540, 2967, 9468, 20790, 34846, 46805, 49335, 30880
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OFFSET
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0,5
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COMMENTS
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A triangulation is simple if it contains no separating 3-cycle. There are n interior nodes and m+3 nodes on the boundary. - Andrew Howroyd, Feb 24 2021
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LINKS
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FORMULA
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G.f. of row m > 0: R(x) satisfies g(x^2)^(m+1)*R(x*g(x^2)) = B(x^2) where g(x) is the g.f. of column 0 of A341856 and B(x) is the g.f. of column m of A341856.
G.f. of row m > 0: h(x)^(m+1)*B(x*h(x)^2) where 2-h(x) is the g.f. of A000256 and B(x) is the g.f. of column m of A341856.
(End)
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EXAMPLE
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Array begins:
1, 2, 6, 22, 91, ...
1, 5, 20, 85, 385, ...
1, 9, 50, 254, 1287, ...
1, 14, 105, 644, 3696, ...
1, 20, 196, 1448, 9468, ...
...
The array transposed for comparability with A341856 begins:
==================================================
n\m | 0 1 2 3 4 5 6
----+---------------------------------------------
1 | 1 1 1 1 1 1 1 ...
2 | 0 2 5 9 14 20 27 ...
3 | 1 6 20 50 105 196 336 ...
4 | 3 22 85 254 644 1448 2967 ...
5 | 12 91 385 1287 3696 9468 22131 ...
6 | 52 408 1836 6630 20790 58564 151146 ...
7 | 241 1938 9120 34846 116641 353056 983664 ...
(End)
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PROG
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H(n)={my(g=1+serreverse(x/(1+x)^4 + O(x*x^n) )); 2 - sqrt(serreverse(x*(2-g)^2*g^4)/x)}
U(n, m)={(3*(m+2)!*(m-1)!/(3*n+3*m+3)!)*sum(j=0, min(m, n-1), (4*n+3*m-j+1)!*(m+j+2)*(m-3*j)/(j!*(j+1)!*(m-j)!*(m-j+2)!*(n-j-1)!))}
R(N, m)={my(g=2-H(N)); Vec(if(m==0, 1-g, g^(m+1)*subst(O(x*x^N) + sum(n=1, N, U(n, m)*x^n), x, x*g^2)))}
M(m, n=m)={Mat(vectorv(m+1, i, R(n, i-1)))}
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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