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A127167
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T(3n,2n), where T is the array in A047110.
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1
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1, 5, 73, 1348, 27811, 612728, 14103464, 334974405, 8146520511, 201822398131, 5074951075766, 129185072614240, 3322359273912432, 86191998671455630, 2252923797781463037, 59273686760263160137, 1568440076774389559527, 41713725234702452284249
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: A(x) where (161051*x^2 +1088*x -64) * A(x)^10 + (4600*x -320) * A(x)^9 + (7276*x -624) * A(x)^8 + (7830*x -512) * A(x)^7 + (6189*x +68) * A(x)^6 + (2177*x + 540) * A(x)^5 + 535*A(x)^4 + 278*A(x)^3 + 84*A(x)^2 + 14*A(x) + 1 = 0. - Mark van Hoeij, May 01 2013
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EXAMPLE
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T(h,k) counts lattice paths restricted as in A047110 by the line y=2x/3, so that the numbers T(3n,2n) are of interest.
T(3,2) counts these 5 paths: RRRUU, RRURU, URRRU, URURR, UURRR.
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MAPLE
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T:= proc(h, k) option remember;
`if`([h, k]=[0, 0], 1, `if`(h<0 or k<0, 0, T(h-1, k)+
`if`(3*k>2*h and 3*(k-1)<2*h, 0, T(h, k-1))))
end:
a:= n-> T(3*n, 2*n):
series(RootOf((161051*x^2+1088*x-64)*A^10 + (4600*x-320)*A^9 + (7276*x-624)*A^8 + (7830*x-512)*A^7 + (6189*x+68)*A^6 + (2177*x+540)*A^5 +535*A^4 +278*A^3 +84*A^2 +14*A +1, A), x=0, 30); # Mark van Hoeij, May 01 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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