|
|
A009119
|
|
Expansion of e.g.f. cos(x/cosh(x)) (even powers only).
|
|
4
|
|
|
1, -1, 13, -301, 11705, -698521, 59340997, -6782462597, 1000434618609, -184576848771889, 41577074746699261, -11216502744649033437, 3567416307426404300713, -1320192785381894987925961, 562163981454375064332029365, -272809563505907130928868599861
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
LINKS
|
|
|
FORMULA
|
a(n) = 2*Sum_{k=1..n-1} binomial(2*n,2*k)*Sum_{j=0..(n-k)} binomial(k+j-1,j)*4^(n-k-j)*Sum_{i=0..j} (i-j)^(2*n-2*k)*binomial(2*j,i)*(-1)^(k+j-i) +(-1)^n. - Vladimir Kruchinin, Jun 16 2011
|
|
MATHEMATICA
|
With[{nn=30}, Take[CoefficientList[Series[Cos[x/Cosh[x]], {x, 0, nn}], x] Range[ 0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jul 07 2017 *)
|
|
PROG
|
(Maxima)
a(n):=2*sum(binomial(2*n, 2*k)*sum(binomial(k+j-1, j)*4^(n-k-j)*sum((i-j)^(2*n-2*k)*binomial(2*j, i)*(-1)^(k+j-i), i, 0, j), j, 0, (n-k)), k, 1, n-1)+(-1)^n; /* Vladimir Kruchinin, Jun 16 2011 */
(PARI) x='x+O('x^50); v=Vec(serlaplace(cos(x/cosh(x)))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 26 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
sign
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|