A008737 a(n) = floor(n/6)*ceiling(n/6).

0, 0, 0, 0, 0, 0, 1, 2, 2, 2, 2, 2, 4, 6, 6, 6, 6, 6, 9, 12, 12, 12, 12, 12, 16, 20, 20, 20, 20, 20, 25, 30, 30, 30, 30, 30, 36, 42, 42, 42, 42, 42, 49, 56, 56, 56, 56, 56, 64, 72, 72, 72, 72, 72, 81, 90, 90, 90, 90, 90, 100

Offset

0,8

Links

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

Index entries for linear recurrences with constant coefficients, signature (2, -2, 2, -2, 2, 0, -2, 2, -2, 2, -2, 1).

Formula

G.f.: x^6/((1-x)^3*(1+x)*(1+x^2+x^4)^2). - G. C. Greubel, Jul 30 2019

Mathematica

Table[Floor[n/6] Ceiling[n/6], {n, 0, 70}] (* Vincenzo Librandi, Dec 19 2016 *)

Prog

(Magma) [Floor(n/6)*Ceiling(n/6): n in [0..70]]; // Vincenzo Librandi, Dec 19 2016
(PARI) vector(70, n, n--; (n\6)*ceil(n/6)) \\ G. C. Greubel, Jul 30 2019
(Magma) [Floor(n/6)*Ceiling(n/6): n in [0..70]]; // G. C. Greubel, Jul 30 2019
(Sage) [floor(n/6)*ceil(n/6) for n in (0..70)] # G. C. Greubel, Jul 30 2019
(GAP) a:=[0, 0, 0, 0, 0, 0, 1, 2, 2, 2, 2, 2];; for n in [13..70] do a[n]:=2*(a[n-1] -a[n-2]+a[n-3]-a[n-4]+a[n-5]-a[n-7]+a[n-8]-a[n-9]+a[n-10]-a[n-11]) + a[n-12]; od; a; # G. C. Greubel, Jul 30 2019

Crossrefs

Sequence in context: A327817 A353643 A168260 * A244460 A160419 A152659

Adjacent sequences: A008734 A008735 A008736 * A008738 A008739 A008740

Keyword

nonn

Author

N. J. A. Sloane

Status

approved