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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, 1, 6, 12, 24, 40, 1008, 3360, 362880, 181440, 39916800, 15966720, 6227020800, 32947200, 261534873600, 373621248000, 2845499424768, 88921857024000, 121645100408832000, 1422749712384000, 3005349539512320000, 10218188434341888000, 25852016738884976640000 (list; graph; refs; listen; history; text; internal format)
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: A124509 A319127 A063104 * A199910 A210678 A304938

Adjacent sequences:  A090762 A090763 A090764 * A090766 A090767 A090768

KEYWORD

nonn,frac

AUTHOR

N. J. A. Sloane, Feb 08 2004

STATUS

approved

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Last modified March 28 15:09 EDT 2020. Contains 333089 sequences. (Running on oeis4.)