A213036 a(n) = n^2 - floor(2n/3)^2.

0, 1, 3, 5, 12, 16, 20, 33, 39, 45, 64, 72, 80, 105, 115, 125, 156, 168, 180, 217, 231, 245, 288, 304, 320, 369, 387, 405, 460, 480, 500, 561, 583, 605, 672, 696, 720, 793, 819, 845, 924, 952, 980, 1065, 1095, 1125, 1216, 1248, 1280, 1377, 1411

Offset

0,3

Links

Table of n, a(n) for n=0..50.

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

Formula

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

G.f.: (x^2)*(x + 2*x^2 + 2*x^3 + 5*x^4)/((1 - x)^3*(1 + x + x^2)^2).

Mathematica

a[n_] := n^2 - Floor[2 n/3]^2
Table[a[n], {n, 0, 90}]    (* A213036 *)

Crossrefs

Sequence in context: A151866 A269928 A057587 * A032438 A025083 A203150

Adjacent sequences: A213033 A213034 A213035 * A213037 A213038 A213039

Keyword

nonn,easy

Author

Clark Kimberling, Jun 06 2012

Status

approved