A027913 T(n,[ n/2 ]), T given by A027907.

1, 1, 2, 3, 10, 15, 50, 77, 266, 414, 1452, 2277, 8074, 12727, 45474, 71955, 258570, 410346, 1481108, 2355962, 8533660, 13599915, 49402850, 78855339, 287134346, 458917850, 1674425300, 2679183405, 9792273690, 15683407785

Offset

0,3

Comments

The median coefficient in the expansion of (1 + x + x^2)^n. - Vladimir Reshetnikov, Nov 21 2020

Links

Robert Israel, Table of n, a(n) for n = 0..2550

Formula

a(n) = GegenbauerC(floor(n/2), -n, -1/2). - Emanuele Munarini, Oct 18 2016

G.f.: g(t) = (1+(t+t^2)*A(t^2)+t^4*A(t^2)^2)/(1-t^2*A(t^2)-3*t^4*A(t^2)^2), where A(t) is the g.f. of A143927 and satisfies A(t) = [1 + x*A(t) + t^2*A(t)^2]^2. - Emanuele Munarini, Oct 20 2016

Maple

seq(simplify(GegenbauerC(floor(n/2), -n, -1/2)), n=0..100); # Robert Israel, Oct 20 2016

Mathematica

Table[GegenbauerC[Floor[n/2], -n, -1/2] + KroneckerDelta[n, 0], {n, 0,
100}] (* Emanuele Munarini, Oct 20 2016 *)

Prog

(Maxima) makelist(ultraspherical(floor(n/2), -n, -1/2), n, 0, 12); /* Emanuele Munarini, Oct 18 2016 */

Crossrefs

Cf. A027907, A027908.

Sequence in context: A226881 A369781 A026336 * A081204 A293308 A357269

Adjacent sequences: A027910 A027911 A027912 * A027914 A027915 A027916

Keyword

nonn

Author

Clark Kimberling

Status

approved