OFFSET
1,2
FORMULA
a(n) ~ (n-1)!/r^n, where r = 0.73908513321516... is the root of the equation r = cos(r). - Vaclav Kotesovec, Jun 27 2013
EXAMPLE
E.g.f.: A(x) = x + 2*x^2/2! + 5*x^3/3! + 20*x^4/4! + 109*x^5/5! + 736*x^6/6! +...
such that
exp(-A(x)) = 1 - x - x^2/2! + x^4/4! - x^6/6! + x^8/8! - x^10/10! +...
MATHEMATICA
CoefficientList[Series[-Log[Cos[x]-x], {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Jun 27 2013 *)
PROG
(PARI) {a(n)=n!*polcoeff(-log(cos(x+x*O(x^n))-x), n)}
for(n=1, 30, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 08 2012
STATUS
approved