A011875 - OEIS

A011875

a(n) = floor(n*(n-1)/22).

0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 34, 36, 39, 42, 45, 48, 51, 54, 57, 60, 63, 67, 70, 74, 78, 82, 86, 90, 94, 98, 102, 106, 111, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 166, 171, 177, 183, 189, 195, 201, 207

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OFFSET

0,9

LINKS

Table of n, a(n) for n=0..68.

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

MATHEMATICA

Table[Floor[(n(n-1))/22], {n, 0, 70}] (* or *) LinearRecurrence[{2, -1, 0, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1}, {0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 4, 5, 6}, 70]

CROSSREFS

Sequence in context: A093668 A026501 A000926 * A249575 A053433 A091401

Adjacent sequences: A011872 A011873 A011874 * A011876 A011877 A011878

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved