A213034 a(n) = floor(3*n/2)*floor(n/3).

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

Links

Table of n, a(n) for n=0..52.

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

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

Adjacent sequences: A213031 A213032 A213033 * A213035 A213036 A213037

Keyword

nonn,easy

Author

Clark Kimberling, Jun 05 2012

Status

approved