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 A049061 Triangle a(n,k) (1<=k<=n) of "signed Eulerian numbers" read by rows. 6
 1, 1, -1, 1, 0, -1, 1, -1, -1, 1, 1, 2, -6, 2, 1, 1, 1, -8, 8, -1, -1, 1, 8, -19, 0, 19, -8, -1, 1, 7, -27, 19, 19, -27, 7, 1, 1, 22, -32, -86, 190, -86, -32, 22, 1, 1, 21, -54, -54, 276, -276, 54, 54, -21, -1, 1, 52, 27, -648, 1002, 0, -1002, 648, -27, -52, -1, 1, 51, -25 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,12 COMMENTS Identical to rows n=2..n of D(n,k) on page 2 of Tanimoto reference. - Jonathan Vos Post, Dec 11 2006 LINKS Reinhard Zumkeller, Rows n = 1..120 of triangle, flattened J. Desarmenien and D. Foata, The signed Eulerian Numbers J. Desarmenien and D. Foata, The signed Eulerian numbers, Discrete Math. 99 (1992), no. 1-3, 49-58. Shinji Tanimoto, Parity-Alternate Permutations and Signed Eulerian Numbers, arXiv:math/0612135 [math.CO], 2006. S. Tanimoto, A new approach to signed Eulerian numbers, arXiv:math/0602263 [math.CO], 2006. FORMULA a(2n, k) = a(2n-1, k) - a(2n-1, k-1), a(2n+1, k) = k*a(2n, k) + (2n-k+2)*a(2n, k-1). EXAMPLE Triangle begins:   1;   1, -1;   1,  0, -1;   1, -1, -1,  1;   1,  2, -6,  2,  1;   ... MATHEMATICA a[n_ /; EvenQ[n] && n > 0, k_] := a[n, k] = a[n - 1, k] - a[n - 1, k - 1]; a[n_ /; OddQ[n] && n > 0, k_] := a[n, k] = k*a[n - 1, k] + (n - k + 1)*a[n - 1, k - 1]; a[0, _]=0; a[1, 1]=1; Flatten[Table[a[n, k], {n, 12}, {k, n}]] (* Jean-François Alcover, May 02 2011 *) PROG (Haskell) a049061 n k = a049061_tabl !! (n-1) !! (k-1) a049061_row n = a049061_tabl !! (n-1) a049061_tabl = map fst \$ iterate t ([1], 1) where    t (row, k) = (if odd k then us else vs, k + 1) where      us = zipWith (-) (row ++ [0]) ([0] ++ row)      vs = zipWith (+) ((zipWith (*) ks row) ++ [0])                       ([0] ++ (zipWith (*) (reverse ks) row))           where ks = [1..k] -- Reinhard Zumkeller, Jan 30 2013 CROSSREFS Cf. A008292. Cf. A080856. Sequence in context: A168294 A004544 A010590 * A342670 A298782 A082516 Adjacent sequences:  A049058 A049059 A049060 * A049062 A049063 A049064 KEYWORD sign,easy,tabl,nice AUTHOR EXTENSIONS More terms from Larry Reeves (larryr(AT)acm.org), Apr 12 2000 ArXiv URL replaced by its non-cached version - R. J. Mathar, Oct 23 2009 STATUS approved

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Last modified April 12 03:14 EDT 2021. Contains 342912 sequences. (Running on oeis4.)