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A173993
Sequence whose Hankel transform is the Somos (4) sequence.
1
1, 2, 6, 17, 50, 146, 430, 1267, 3746, 11091, 32900, 97716, 290586, 864980, 2577032, 7683397, 22922874, 68427057, 204362172, 610604629, 1825092080, 5457016431, 16321318264, 48828168580, 146112907266, 437319580738, 1309158060068
OFFSET
0,2
COMMENTS
Hankel transform is A006720(n+3).
LINKS
FORMULA
G.f.: (sqrt((1-2x)*(1-2x-4x^2+4x^3))-2x^2+4x-1)/(2x*(1-4x+3x^2)).
Conjecture: (n+1)*a(n) +2*(-4*n-1)*a(n-1) +(19*n-5)*a(n-2) -36*a(n-3) +8*(-7*n+26)*a(n-4) +2*(34*n-143)*a(n-5) +24*(-n+5)*a(n-6)=0. - R. J. Mathar, Oct 10 2014
MATHEMATICA
CoefficientList[Series[(Sqrt[(1-2*x)*(1-2*x-4*x^2+4*x^3)]-2*x^2+4*x-1)/( 2 x*(1 - 4 x + 3 x^2)), {x, 0, 50}], x] (* G. C. Greubel, Sep 22 2018 *)
PROG
(PARI) my(x='x+O('x^50)); Vec((sqrt((1-2*x)*(1-2*x-4*x^2+4*x^3))-2*x^2+4*x-1)/(2*x*(1-4*x+3*x^2))) \\ G. C. Greubel, Sep 22 2018
(Magma) m:=50; R<x>:=PowerSeriesRing(Rationals(), m); Coefficients(R!((Sqrt((1-2*x)*(1-2*x-4*x^2+4*x^3))-2*x^2+4*x-1)/(2*x*(1-4*x+3*x^2)))); // G. C. Greubel, Sep 22 2018
CROSSREFS
Sequence in context: A244405 A244406 A244407 * A270863 A027914 A098703
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Mar 04 2010
STATUS
approved