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 A178964 E.g.f.: (1+sqrt(2)*sin(x/sqrt(2))*cosh(x/sqrt(2))+sin(x/sqrt(2))*sinh(x/sqrt(2)))/(cos(x/sqrt(2))*cosh(x/sqrt(2))). 5
 1, 1, 1, 1, 1, 4, 14, 34, 69, 496, 2896, 11056, 33661, 349504, 2856944, 14873104, 60376809, 819786496, 8615785216, 56814228736, 288294050521, 4835447317504, 62112775514624, 495812444583424, 3019098162602349, 60283564499562496, 915153344223809536, 8575634961418940416, 60921822444067346581, 1411083019275488149504, 24716980773496372066304 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 COMMENTS According to Mendes and Remmel, p. 56, this is the e.g.f. for 4-alternating permutations. REFERENCES Anthony Mendes and Jeffrey Remmel, Generating functions from symmetric functions, Preliminary version of book, available from Jeffrey Remmel's home page http://math.ucsd.edu/~remmel/ LINKS Alois P. Heinz, Table of n, a(n) for n = 0..200 J. M. Luck, On the frequencies of patterns of rises and falls, arXiv:1309.7764, 2014 Peter Luschny, An old operation on sequences: the Seidel transform FORMULA a(n) ~ n! * 2^(n/2+1) * (-sqrt(2)*(-1+(-1)^n) - 2*cos(n*Pi/2)*(sinh(Pi/2)-1)/cosh(Pi/2) + (1+(-1)^n)*(1 + sinh(Pi/2))/cosh(Pi/2)) / Pi^(n+1). - Vaclav Kotesovec, Sep 09 2014 MAPLE A178964_list := proc(dim) local E, DIM, n, k; DIM := dim-1; E := array(0..DIM, 0..DIM); E[0, 0] := 1; for n from 1 to DIM do if n mod 4 = 0 then E[n, 0] := 0 ;    for k from n-1 by -1 to 0 do E[k, n-k] := E[k+1, n-k-1] + E[k, n-k-1] od; else E[0, n] := 0;    for k from 1 by 1 to n do E[k, n-k] := E[k-1, n-k+1] + E[k-1, n-k] od; fi od; [E[0, 0], seq(E[k, 0]+E[0, k], k=1..DIM)] end: A178964_list(31); # Peter Luschny, Apr 02 2012 # Alternatively, using a bivariate exponential generating function: A178964 := proc(n) local g, p, q; g := (x, z) -> 2*exp(x*z)/(cosh(z)+cos(z)); p := (n, x) -> n!*coeff(series(g(x, z), z, n+2), z, n); q := (n, m) -> if modp(n, m) = 0 then 0 else 1 fi: (-1)^binomial(n, 4)*p(n, q(n, 4)) end: seq(A178964(i), i=0..30); # Peter Luschny, Jun 06 2012 MATHEMATICA max = 30; s = Series[Sec[x]*Sech[x]+Tan[x]*(Sqrt[2]+Tanh[x]) /. x -> x/Sqrt[2], {x, 0, max+1}]; a[n_] := SeriesCoefficient[s, {x, 0, n}]*n!; Table[a[n], {n, 0, max}] (* Jean-François Alcover, Feb 25 2014 *) PROG (Sage) # Function A(m, n) defined in A181936. A178964 = lambda n: (-1)^int(is_odd(n//4))*A(4, n) print [A178964(n) for n in (0..30)] # Peter Luschny, Jan 24 2017 (PARI) x='x+O('x^30); round(Vec(serlaplace((1+sqrt(2)*sin(x/sqrt(2))*cosh( x/sqrt(2)) + sin(x/sqrt(2))*sinh(x/sqrt(2)))/(cos(x/sqrt(2))*cosh(x/sqrt(2)))))) CROSSREFS Number of m-alternating permutations: A000012 (m=1), A000111 (m=2), A178963 (m=3), A178964 (m=4), A181936 (m=5). Cf. A181937. Sequence in context: A099586 A253001 A063258 * A197275 A011852 A288678 Adjacent sequences:  A178961 A178962 A178963 * A178965 A178966 A178967 KEYWORD nonn AUTHOR N. J. A. Sloane, Dec 31 2010 STATUS approved

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Last modified March 26 00:20 EDT 2019. Contains 321478 sequences. (Running on oeis4.)