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A144580
Denominators of expansion of exp(1-sqrt(1-x-x^2)).
2
1, 2, 4, 48, 384, 640, 46080, 645120, 1720320, 185794560, 3715891200, 1946419200, 1961990553600, 7287393484800, 238054853836800, 42849873690624000, 1371195958099968000, 7770110429233152000, 239763407530622976000, 63777066403145711616000
OFFSET
0,2
COMMENTS
D-finite with recurrence: Expansion satisfies 8*a(n)+12*a(n+1)+(22+8*n^2+24*n)*a(n+2)+(73+12*n^2+60*n)*a(n+3)+(-18*n-8-4*n^2)*a(n+4)+(-4*n^2-36*n-80)*a(n+5)=0. - Robert Israel, Dec 31 2019
LINKS
EXAMPLE
The expansion is 1 + (1/2)*x + (3/4)*x^2 + (31/48)*x^3 + (301/384)*x^4 + (571/640)*x^5 + (51751/46080)*x^6 + ( 926731/645120)*x^7 + (3281851/1720320)*x^8 + ...
MAPLE
g:= gfun:-rectoproc({8*a(n)+12*a(n+1)+(22+8*n^2+24*n)*a(n+2)+(73+12*n^2+60*n)*a(n+3)+(-18*n-8-4*n^2)*a(n+4)+(-4*n^2-36*n-80)*a(n+5), a(0) = 1, a(1) = 1/2, a(2) = 3/4, a(3) = 31/48, a(4) = 301/384}, a(n), remember):
seq(denom(g(n)), n=0..40); # Robert Israel, Dec 31 2019
MATHEMATICA
CoefficientList[Series[Exp[1-Sqrt[1-x-x^2]], {x, 0, 20}], x]//Denominator (* Harvey P. Dale, May 09 2023 *)
CROSSREFS
Cf. A144579.
Sequence in context: A212429 A298903 A127211 * A144578 A143968 A308665
KEYWORD
nonn,frac
AUTHOR
N. J. A. Sloane, Jan 07 2009
STATUS
approved