A090765 Let f(0) = 0, f(1) = 1 and for n > 1 let f(n) = (-1)*sum((-1)^(n+r)*f(r),r=0..n-2)/(n*(n-1)); sequence gives denominator of f(n).

1, 1, 1, 6, 12, 24, 40, 1008, 3360, 362880, 181440, 39916800, 15966720, 6227020800, 32947200, 261534873600, 373621248000, 2845499424768, 88921857024000, 121645100408832000, 1422749712384000, 3005349539512320000, 10218188434341888000, 25852016738884976640000

Offset

0,4

Comments

G.f. y=Sum_{k>0} f(n)x^n satisfies y''+y/(1+x)=0. - Michael Somos, Feb 14 2004

References

H. K. Wilson, Ordinary Differential Equations, Addison-Wesley, 1971, p. 154.

Links

Table of n, a(n) for n=0..23.

Example

Sequence f(n) begins 0, 1, 0, -1/6, 1/12, -1/24, 1/40, -17/1008, 41/3360, ...

Prog

(PARI) a(n)=local(y); if(n<0, 0, y=O(x); for(k=1, n, y=x+intformal(intformal(-y/(1+x)))); denominator(polcoeff(y, n)))

Crossrefs

Cf. A090295.

Sequence in context: A319127 A367099 A063104 * A199910 A210678 A358508

Adjacent sequences: A090762 A090763 A090764 * A090766 A090767 A090768

Keyword

nonn,frac

Author

N. J. A. Sloane, Feb 08 2004

Status

approved