A011862 a(n) = floor(n*(n-1)/9).

0, 0, 0, 0, 1, 2, 3, 4, 6, 8, 10, 12, 14, 17, 20, 23, 26, 30, 34, 38, 42, 46, 51, 56, 61, 66, 72, 78, 84, 90, 96, 103, 110, 117, 124, 132, 140, 148, 156, 164, 173, 182, 191, 200, 210, 220, 230, 240, 250, 261, 272, 283, 294, 306, 318, 330, 342, 354, 367, 380, 393, 406, 420

Offset

0,6

Links

Table of n, a(n) for n=0..62.

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

Formula

From R. J. Mathar, Apr 15 2010: (Start)

G.f.: x^4*(1 + x^4)/ ((1 - x)^3*(1 + x + x^2)*(1 + x^3 + x^6)).

a(n) = 2*a(n-1) - a(n-2) + a(n-9) - 2*a(n-10) + a(n-11). (End)

Mathematica

Table[Floor[(n(n-1))/9], {n, 0, 70}] (* or *) LinearRecurrence[{2, -1, 0, 0, 0, 0, 0, 0, 1, -2, 1}, {0, 0, 0, 0, 1, 2, 3, 4, 6, 8, 10}, 70] (* Harvey P. Dale, Oct 01 2017 *)

Crossrefs

Sequence in context: A097602 A347625 A126794 * A122957 A078769 A064375

Adjacent sequences: A011859 A011860 A011861 * A011863 A011864 A011865

Keyword

nonn,easy

Author

N. J. A. Sloane.

Status

approved