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A213034
a(n) = floor(3*n/2)*floor(n/3).
1
0, 0, 0, 4, 6, 7, 18, 21, 24, 40, 45, 49, 72, 78, 84, 112, 120, 127, 162, 171, 180, 220, 231, 241, 288, 300, 312, 364, 378, 391, 450, 465, 480, 544, 561, 577, 648, 666, 684, 760, 780, 799, 882, 903, 924, 1012, 1035, 1057, 1152, 1176, 1200, 1300, 1326
OFFSET
0,4
FORMULA
a(n) = a(n-1)+a(n-3)-a(n-4)+a(n-6)-a(n-7)-a(n-9)+a(n-10).
G.f.: (4*x^3 + 2*x^4 + x^5 + 7*x^6 + x^7 + 2*x^8 + x^9)/(1 - x - x^3 + x^4 - x^6 + x^7 + x^9 - x^10).
MATHEMATICA
a[n_] := Floor[(3 n/2)*Floor[n/3]]
Table[a[n], {n, 0, 90}] (* A213034 *)
LinearRecurrence[{1, 0, 1, -1, 0, 1, -1, 0, -1, 1}, {0, 0, 0, 4, 6, 7, 18, 21, 24, 40}, 90]
CROSSREFS
Sequence in context: A107919 A165404 A270887 * A102131 A102137 A102135
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jun 05 2012
STATUS
approved