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Search: id:A110440
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| A110440 |
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Triangular array formed by the little Schroeder numbers. s(n,k)= the number of unit step restricted paths (i.e. they never go below the x-axis) from the origin (0,0) to (n-1,k-1) using up step U(1,1), three types of level steps L(1,0),L'(1,0),L"(1,0) and two types of down steps D(1,-1),D'(1,-1). s(0,0)=1 and the leftmost column s(n,0) is A001003. |
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+0
3
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| 1, 3, 1, 11, 6, 1, 45, 31, 9, 1, 197, 156, 60, 12, 1, 903, 785, 360, 98, 15, 1, 4279, 3978, 2061, 684, 145, 18, 1, 20793, 20335, 11529, 4403, 1155, 201, 21, 1, 103049, 104856, 63728, 27048, 8270, 1800, 266, 24, 1, 518859, 545073, 350136, 161412, 55458, 14202
(list; table; graph; listen)
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OFFSET
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0,2
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COMMENT
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This sequence factors A038255 into a product of Riordan arrays.
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REFERENCES
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Naiomi T. Cameron and Asamoah Nkwanta, On Some (Pseudo) Involutions in the Riordan Group, Journal of Integer Sequences, Vol. 8 (2005), Article 05.3.7.
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FORMULA
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Recurrence is s(n+1, 0)= 3s(n, k)+ 2s(n, k+1) for the leftmost column entries and s(n+1, k)= s(n, k-1)+ 3s(n, k)+ 2s(n, k+1) for the other column entries. Riordan array ((1-3z-sqrt(1-6z+z^2))/4z*z, (1-3z-sqrt(1-6z+z^2))/4z)
Sum_{k, k>=0} T(m, k)*T(n, k)*2^k = T(m+n, 0) = A001003(m+n+1) . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Sep 14 2005
G.f.: 2/( 1 -x*L -2*x*y*U + sqrt( (1 -x*L)^2 -4*x^2*D*U ) ) where L=3, U=1, D=2. - Michael Somos Mar 31 2007
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EXAMPLE
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Triangle starts:
1;
3,1;
11,6,1;
45,31,9,1;
197,156,60,12,1; ...
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PROGRAM
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(PARI) {T(n, k)= if(n<0| k>n, 0, polcoeff(polcoeff( 2/(1 -3*x -2*x*y +sqrt( 1 -6*x +x^2 +x*O(x^n)) ), n), k))} /* Michael Somos Mar 31 2007 */
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CROSSREFS
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Sequence in context: A113955 A110165 A111965 this_sequence A135574 A008969 A119908
Adjacent sequences: A110437 A110438 A110439 this_sequence A110441 A110442 A110443
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KEYWORD
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easy,nice,nonn,tabl
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AUTHOR
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Asamoah Nkwanta (nkwanta(AT)jewel.morgan.edu), Aug 08 2005
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