A079514 Second column of triangular array in A079513.

1, 1, 3, 6, 22, 53, 211, 554, 2306, 6362, 27230, 77580, 338444, 986253, 4362627, 12927170, 57788170, 173452334, 781825066, 2370742868, 10757497972, 32892031042, 150073096238, 462030186916, 2117778107732, 6557906929108, 30176799215196, 93909078262808

Offset

1,3

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

D. Merlini, R. Sprugnoli and M. C. Verri, The tennis ball problem, J. Combin. Theory, A 99 (2002), 307-344 (Table A.2).

Formula

G.f.: 2*(1-sqrt(1-4*x))/(2+sqrt(1-4*x)+sqrt(1+4*x)). - Philippe Deléham, Feb 09 2014

Mathematica

Rest[CoefficientList[Series[2*(1-Sqrt[1-4*x])/(2+Sqrt[1-4*x] +Sqrt[1+ 4*x]), {x, 0, 30}], x]] (* G. C. Greubel, Jan 15 2019 *)

Prog

(PARI) my(x='x+O('x^30)); Vec(2*(1-sqrt(1-4*x))/(2+sqrt(1-4*x) +sqrt(1 +4*x))) \\ G. C. Greubel, Jan 15 2019
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); Coefficients(R!( 2*(1-Sqrt(1-4*x))/(2+Sqrt(1-4*x)+Sqrt(1+4*x)) )); // G. C. Greubel, Jan 15 2019
(Sage) a=(2*(1-sqrt(1-4*x))/(2+sqrt(1-4*x)+sqrt(1+4*x))).series(x, 30).coefficients(x, sparse=False); a[1:] # G. C. Greubel, Jan 15 2019

Crossrefs

Sequence in context: A295578 A054297 A325158 * A148624 A148625 A148626

Adjacent sequences: A079511 A079512 A079513 * A079515 A079516 A079517

Keyword

nonn

Author

N. J. A. Sloane, Jan 22 2003

Extensions

More terms from Philippe Deléham, Feb 09 2014

Status

approved