A232493 If n mod 2 = 0 then 2^n*3^(n-1)+2^(n+1)*3^(n/2-1) otherwise 2^n*3^(n-1)+2^n*3^((n-1)/2).

1, 4, 20, 96, 528, 2880, 16704, 96768, 573696, 3400704, 20321280, 121430016, 727584768, 4359536640, 26145275904, 156799991808, 940656623616, 5643079778304, 33856758743040, 203130232897536, 1218760758263808, 7312440714854400, 43874396619669504, 263244893701275648, 1579466390174171136

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

G. Wu, M. G. Parker, A complementary construction using mutually unbiased bases, arXiv preprint arXiv:1309.0157 [cs.IT], 2013 [See Th. 1].

Index entries for linear recurrences with constant coefficients, signature (6,12,-72).

Formula

G.f.: ( 1-2*x-16*x^2 ) / ( (6*x-1)*(12*x^2-1) ). - R. J. Mathar, Dec 04 2013

Maple

f:=proc(n)
if (n mod 2) = 0 then 2^n*3^(n-1)+2^(n+1)*3^(n/2-1) else
2^n*3^(n-1)+2^n*3^((n-1)/2) fi; end;
[seq(f(n), n=0..40)];

Mathematica

LinearRecurrence[{6, 12, -72}, {1, 4, 20}, 40] (* Harvey P. Dale, May 03 2017 *)
CoefficientList[Series[(1 - 2 x - 16 x^2)/((6 x - 1) (12 x^2 - 1)), {x, 0, 33}], x] (* Vincenzo Librandi, May 07 2017 *)

Prog

(Magma) I:=[1, 4, 20]; [n le 3 select I[n] else 6*Self(n-1)+12*Self(n-2)-72*Self(n-3): n in [1..30]]; // Vincenzo Librandi, May 07 2017

Crossrefs

Sequence in context: A296665 A057087 A151254 * A240778 A293710 A098225

Adjacent sequences: A232490 A232491 A232492 * A232494 A232495 A232496

Keyword

nonn

Author

N. J. A. Sloane, Dec 02 2013

Status

approved