A011864 - OEIS

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A011864

a(n) = floor(n*(n - 1)/11).

0, 0, 0, 0, 1, 1, 2, 3, 5, 6, 8, 10, 12, 14, 16, 19, 21, 24, 27, 31, 34, 38, 42, 46, 50, 54, 59, 63, 68, 73, 79, 84, 90, 96, 102, 108, 114, 121, 127, 134, 141, 149, 156, 164, 172, 180, 188, 196, 205, 213, 222, 231, 241, 250, 260, 270, 280, 290, 300, 311, 321, 332, 343, 355

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,7

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

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

FORMULA

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

a(n) = 2*a(n - 1) - a(n - 2) + a(n - 11) - 2*a(n - 12) + a(n - 13).

G.f.: x^4*(x^2 - x + 1)*(1 + x^4)/ ((1 - x)^3 * (1 + x + x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^10)). (End)

MATHEMATICA

LinearRecurrence[{2, -1, 0, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1}, {0, 0, 0, 0, 1, 1, 2, 3, 5, 6, 8, 10, 12}, 64] (* Peter Luschny, Aug 13 2021 *)