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 A000718 Boustrophedon transform of triangular numbers 1,1,3,6,10,... 4
 1, 2, 6, 20, 65, 226, 883, 3947, 20089, 115036, 732171, 5126901, 39165917, 324138010, 2888934623, 27587288507, 281001801969, 3041152133848, 34849036364659, 421526126267265, 5367037330561365, 71752003756908550 (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 E.g.f.: (sec(x)+tan(x))*(exp(x)*(x+1/2*x^2)+1). - Sergei N. Gladkovskii, Oct 30 2014 a(n) ~ n! * (8 + exp(Pi/2)*Pi*(4+Pi)) * 2^(n-1) / Pi^(n+1). - Vaclav Kotesovec, Jun 12 2015 MATHEMATICA t[n_, 0] := If[n == 0, 1, n*(n+1)/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) a000718 n = sum \$ zipWith (*) (a109449_row n) (1 : tail a000217_list) -- Reinhard Zumkeller, Nov 04 2013 CROSSREFS Cf. A109449, A000217, A000746. Sequence in context: A302612 A005726 A148473 * A148474 A156831 A027061 Adjacent sequences:  A000715 A000716 A000717 * A000719 A000720 A000721 KEYWORD nonn AUTHOR STATUS approved

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Last modified December 10 00:30 EST 2018. Contains 318032 sequences. (Running on oeis4.)