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 A001759 Number of permutations of [n] with n-3 sequences. (Formerly M2150 N0857) 2
 2, 28, 236, 1852, 14622, 119964, 1034992, 9434444, 90968602, 927367340, 9982234068, 113261721276, 1352111669942, 16950982295356, 222752212005464, 3062768908594348, 43987314357078642, 658804420084315212 (list; graph; refs; listen; history; text; internal format)
 OFFSET 4,1 REFERENCES L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 261. N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS FORMULA From Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Mar 12 2001: (Start) E.g.f.: (1/2)*u(x)^3+(11/2)*u(x)-2*u(x)^2-(x/2)*u(x)^2+x/2, where u(x)=sec(x)+tan(x), n>3. a(n) ~ 2n!(2/Pi)^(n+1)((4n^2+12n+8)/(Pi^2)-8(n+1)/Pi+5-n). (End) E.g.f.: (5 * cos(x) + 2*x * sin(x) - 3*x - 4) / (1 - sin(x)) + (1 + sin(x)) / ((1 - sin(x)) * cos(x)) - 2. - Michael Somos, Aug 28 2012 a(n) = (1/2)*A001758(n) - A001758(n-1) - ((n-1)/2)*A001250(n) if n>2. - Michael Somos, Aug 28 2012 EXAMPLE 2*x^4 + 28*x^5 + 236*x^6 + 1852*x^7 + 14622*x^8 + 119964*x^9 + 1034992*x^10 + ... . - Michael Somos, Aug 28 2012 MAPLE seq(coeff(series(2*tan(t)*sec(t)^2+4*sec(t)+5*tan(t)-4*sec(t)*tan(t)-1-4*sec (t)^2-t*sec(t)*tan(t)+2*sec(t)^3-t*sec(t)^2, t, 30), t, i)*i!, i=4..24); # Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Mar 12 2001 CROSSREFS Cf. A001250, A001758. Sequence in context: A035601 A281124 A244721 * A243475 A019441 A147537 Adjacent sequences:  A001756 A001757 A001758 * A001760 A001761 A001762 KEYWORD nonn AUTHOR EXTENSIONS More terms from Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Mar 12 2001 Offset corrected by N. J. A. Sloane, Aug 27 2012 at the suggestion of Michael Somos STATUS approved

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Last modified January 16 13:32 EST 2019. Contains 319193 sequences. (Running on oeis4.)