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 A000746 Boustrophedon transform of triangular numbers. 4
 1, 4, 13, 39, 120, 407, 1578, 7042, 35840, 205253, 1306454, 9148392, 69887664, 578392583, 5155022894, 49226836114, 501420422112, 5426640606697, 62184720675718, 752172431553308, 9576956842743904, 128034481788227195 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 0..400 Peter Luschny, An old operation on sequences: the Seidel transform J. Millar, N. J. A. Sloane and N. E. Young, A new operation on sequences: the Boustrophedon on transform, J. Combin. Theory, 17A 44-54 1996 (Abstract, pdf, ps). N. J. A. Sloane, Transforms Wikipedia, Boustrophedon transform FORMULA a(n) = sum(A109449(n,k)*(k+1)*(k+2)/2: k=0..n). - Reinhard Zumkeller, Nov 03 2013 E.g.f.: (sec(x)+tan(x))*exp(x)*(x^2+4*x+2)/2. - Sergei N. Gladkovskii, Oct 30 2014 a(n) ~ n! * (Pi^2+8*Pi+8) * exp(Pi/2) * 2^(n-1) / Pi^(n+1). - Vaclav Kotesovec, Jun 12 2015 MATHEMATICA t[n_, 0] := (n + 1) (n + 2)/2; t[n_, k_] := t[n, k] = t[n, k - 1] + t[n - 1, n - k]; a[n_] := t[n, n]; Array[a, 30, 0] (* Jean-François Alcover, Feb 12 2016 *) PROG (Haskell) a000746 n = sum \$ zipWith (*) (a109449_row n) \$ tail a000217_list -- Reinhard Zumkeller, Nov 03 2013 CROSSREFS Cf. A000217, A000718. Sequence in context: A290929 A121192 A133409 * A271012 A272581 A191132 Adjacent sequences:  A000743 A000744 A000745 * A000747 A000748 A000749 KEYWORD nonn,changed AUTHOR STATUS approved

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Last modified October 23 11:19 EDT 2019. Contains 328345 sequences. (Running on oeis4.)