A131475 a(n) = floor(n/2) * floor(n^2/2).

0, 0, 2, 4, 16, 24, 54, 72, 128, 160, 250, 300, 432, 504, 686, 784, 1024, 1152, 1458, 1620, 2000, 2200, 2662, 2904, 3456, 3744, 4394, 4732, 5488, 5880, 6750, 7200, 8192, 8704, 9826, 10404, 11664, 12312, 13718, 14440, 16000, 16800

Offset

0,3

Links

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

Index entries for linear recurrences with constant coefficients, signature (1, 3, -3, -3, 3, 1, -1).

Formula

G.f.: 2*x^2*(1 + x + 3*x^2 + x^3)/((1+x)^3*(1-x)^4). - R. J. Mathar, Dec 19 2008

a(n) = a(n-1) + 3*a(n-2) - 3*a(n-3) - 3*a(n-4) + 3*a(n-5) + a(n-6) - a(n-7).

a(n) = A004526(n)*A007590(n). - R. J. Mathar, Mar 04 2018

Prog

(Magma) [Floor(n/2)*Floor(n^2/2): n in [0..60]]; // Vincenzo Librandi, Jun 16 2011

Crossrefs

Cf. A000982, A008619, A004526, A007590.

Sequence in context: A256788 A324211 A059622 * A239363 A045541 A372898

Adjacent sequences: A131472 A131473 A131474 * A131476 A131477 A131478

Keyword

nonn,easy

Author

Mohammad K. Azarian, Jul 27 2007

Status

approved