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A213036
a(n) = n^2 - floor(2n/3)^2.
1
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
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
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jun 06 2012
STATUS
approved