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 A306880 Expansion of e.g.f. (sec(x) + tan(x))/(1 + LambertW(-x)). 2
 1, 2, 7, 44, 401, 4796, 70783, 1240448, 25146113, 578583952, 14892958551, 423979878816, 13225810908881, 448604790288448, 16437893908228367, 647074747622534912, 27233273311687115649, 1220273444664347994368, 57998633082360310382119, 2914426113026062106334720, 154378135436424206699590545 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Boustrophedon transform of A000312. LINKS FORMULA a(n) ~ (1 + sin(exp(-1)))/cos(exp(-1)) * n^n. - Vaclav Kotesovec, Aug 17 2019 MATHEMATICA nmax = 20; CoefficientList[Series[(Sec[x] + Tan[x])/(1 + LambertW[-x]), {x, 0, nmax}], x] Range[0, nmax]! t[n_, 0] := If[n < 1, 1, n^n]; t[n_, k_] := t[n, k] = t[n, k - 1] + t[n - 1, n - k]; a[n_] := t[n, n]; Array[a, 21, 0] CROSSREFS Cf. A000111, A000312, A306881. Sequence in context: A178012 A194018 A196793 * A128579 A194453 A242105 Adjacent sequences:  A306877 A306878 A306879 * A306881 A306882 A306883 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Apr 16 2019 STATUS approved

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Last modified February 24 13:05 EST 2020. Contains 332209 sequences. (Running on oeis4.)