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A163841 Triangle interpolating the swinging factorial (A056040) restricted to even indices with its binomial transform. Same as interpolating bilateral Schroeder paths (A026375) with the central binomial coefficients (A000984). 4
1, 3, 2, 11, 8, 6, 45, 34, 26, 20, 195, 150, 116, 90, 70, 873, 678, 528, 412, 322, 252, 3989, 3116, 2438, 1910, 1498, 1176, 924, 18483, 14494, 11378, 8940, 7030, 5532, 4356, 3432, 86515, 68032, 53538 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

For n >= 0, k >= 0 let T(n,k) = sum{i=k..n} binomial(n-k,n-i)*(2i)$ where i$ denotes the swinging factorial of i (A056040). Triangle read by rows.

REFERENCES

Peter Luschny, "Divide, swing and conquer the factorial and the lcm{1,2,...,n}", preprint, April 2008.

LINKS

G. C. Greubel, Table of n, a(n) for the first 50 rows, flattened

Peter Luschny, Swinging Factorial.

Tony D. Noe, On the Divisibility of Generalized Central Trinomial Coefficients, Journal of Integer Sequences, Vol. 9 (2006), Article 06.2.7.

EXAMPLE

Triangle begins

     1;

     3,    2;

    11,    8,    6;

    45,   34,   26,   20;

   195,  150,  116,   90,   70;

   873,  678,  528,  412,  322,  252;

  3989, 3116, 2438, 1910, 1498, 1176,  924;

MAPLE

Computes n rows of the triangle. For the functions 'SumTria' and 'swing' see A163840.

a := n -> SumTria(k->swing(2*k), n, true);

MATHEMATICA

sf[n_] := n!/Quotient[n, 2]!^2; t[n_, k_] := Sum[Binomial[n - k, n - i]*sf[2*i], {i, k, n}]; Table[t[n, k], {n, 0, 8}, {k, 0, n}] // Flatten (* Jean-Fran├žois Alcover, Jun 28 2013 *)

CROSSREFS

Row sums are A163844. Cf. A056040, A163650, A163841, A163842, A163840, A026375, A002426, A000984.

Sequence in context: A013945 A072656 A191669 * A276589 A275950 A276587

Adjacent sequences:  A163838 A163839 A163840 * A163842 A163843 A163844

KEYWORD

nonn,tabl

AUTHOR

Peter Luschny, Aug 06 2009

STATUS

approved

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Last modified March 27 06:50 EDT 2017. Contains 284144 sequences.