OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..238
FORMULA
a(n) = 2*Sum_{m=0..n-1} binomial(2*n+1,2*m+1)*(Sum_{j=0..(n-m)} binomial(m+j-1/2,j)*4^(n-m-j)*Sum_{i=0..j} (i-j)^(2*n-2*m)* binomial(2*j,i)*(-1)^(m+j-i))) + (-1)^n. - Vladimir Kruchinin, Jun 16 2011
MATHEMATICA
With[{nn=30}, Take[CoefficientList[Series[Sin[x/Cosh[x]], {x, 0, nn}], x] Range[ 0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Dec 24 2017 *)
PROG
(Maxima) a(n):=2*sum(binomial(2*n+1, 2*m+1)*(sum(binomial(m+j-1/2, j)*4^(n-m-j)*sum((i-j)^(2*n-2*m)*binomial(2*j, i)*(-1)^(m+j-i), i, 0, j), j, 0, (n-m))), m, 0, n-1)+(-1)^n; /* Vladimir Kruchinin, Jun 16 2011 */
(PARI) my(x='x+O('x^50)); v=Vec(serlaplace(sin(x/cosh(x)))); vector((#v-1)\2 , n, v[2*n-1]) \\ G. C. Greubel, Jan 21 2018
CROSSREFS
KEYWORD
sign
AUTHOR
EXTENSIONS
Extended with signs by Olivier Gérard, Mar 15 1997
STATUS
approved