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 A106579 Triangular array associated with Schroeder numbers: T(0,0) = 1, T(n,0) = 0 for n > 0; T(n,k) = 0 if k < n; T(n,k) = T(n,k-1) + T(n-1,k-1) + T(n-1,k). 2
 1, 0, 1, 0, 1, 2, 0, 1, 4, 6, 0, 1, 6, 16, 22, 0, 1, 8, 30, 68, 90, 0, 1, 10, 48, 146, 304, 394, 0, 1, 12, 70, 264, 714, 1412, 1806, 0, 1, 14, 96, 430, 1408, 3534, 6752, 8558, 0, 1, 16, 126, 652, 2490, 7432, 17718, 33028, 41586, 0, 1, 18, 160, 938, 4080, 14002, 39152, 89898, 164512, 206098, 0, 1, 20, 198 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 LINKS Reinhard Zumkeller, Rows n = 0..120 of triangle, flattened G. Kreweras, Sur les hiérarchies de segments, Cahiers du Bureau Universitaire de Recherche Opérationnelle, Institut de Statistique, Université de Paris, #20 (1973). G. Kreweras, Sur les hiérarchies de segments, Cahiers du Bureau Universitaire de Recherche Opérationnelle, Institut de Statistique, Université de Paris, #20 (1973). (Annotated scanned copy) FORMULA G.f.: Sum T(n, k)*x^n*y^k = 1 + y*(1 - x*y - (x^2*y^2 - 6*x*y + 1)^(1/2))/(2*y + x*y - 1 + (x^2*y^2 - 6*x*y + 1)^(1/2)). EXAMPLE Triangle starts   1;   0,    1;   0,    1,    2;   0,    1,    4,    6;   0,    1,    6,   16,   22;   0,    1,    8,   30,   68,   90;   0,    1,   10,   48,  146,  304,  394;   0,    1,   12,   70,  264,  714, 1412, 1806;   ... MATHEMATICA T[n_, k_] := T[n, k] = Which[n == k == 0, 1, n == 0, 0, k == 0, 0, k > n, 0, True, T[n, k - 1] + T[n - 1, k - 1] + T[n - 1, k]]; Table[T[n, k], {n, 0, 11}, {k, 0, n}] // Flatten (* Michael De Vlieger, Nov 05 2017 *) PROG (Haskell) a106579 n k = a106579_tabl !! n !! k a106579_row n = a106579_tabl !! n a106579_tabl = [1] : iterate    (\row -> scanl1 (+) \$ zipWith (+) ([0] ++ row) (row ++ [0])) [0, 1] -- Reinhard Zumkeller, Apr 17 2013 (Sage) def A106579_row(n):     if n==0: return [1]     @cached_function     def prec(n, k):         if k==n: return -1         if k==0: return 0         return prec(n-1, k-1)-2*sum(prec(n, k+i-1) for i in (2..n-k+1))     return [(-1)^k*prec(n, n-k+1) for k in (0..n)] for n in (0..10): print A106579_row(n) # Peter Luschny, Mar 16 2016 CROSSREFS Essentially the same as A033877 except with a leading column 1, 0, 0, 0, ... Last diagonal: A006318 or A103137. Row sums give A001003. See A033877 for more comments and references. Sequence in context: A247126 A229223 A128749 * A287318 A173003 A294411 Adjacent sequences:  A106576 A106577 A106578 * A106580 A106581 A106582 KEYWORD nonn,tabl AUTHOR N. J. A. Sloane, May 30 2005 STATUS approved

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Last modified June 19 00:55 EDT 2019. Contains 324217 sequences. (Running on oeis4.)