A011866 - OEIS

A011866

a(n) = floor(n*(n-1)/13).

0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 23, 26, 29, 32, 35, 38, 42, 46, 50, 54, 58, 62, 66, 71, 76, 81, 86, 91, 96, 102, 108, 114, 120, 126, 132, 138, 145, 152, 159, 166, 173, 180, 188, 196, 204, 212, 220, 228, 236, 245, 254, 263, 272, 281, 290, 300, 310

(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,-1,0,0,0,0,0,0,0,0,0,0,1,-2,1).

FORMULA

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

a(n) = 2*a(n-1) - a(n-2) + a(n-13) - 2*a(n-14) + a(n-15).

G.f.: x^5*(1+x^6)/(1+x*(-2+x*(1+x^11*(-1+(2-x)*x)))). (End)

MATHEMATICA

Table[Floor[(n(n-1))/13], {n, 0, 70}] (* or *) LinearRecurrence[{2, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1}, {0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14}, 70] (* Harvey P. Dale, Nov 10 2019 *)

CROSSREFS

Sequence in context: A274039 A005377 A120370 * A392071 A321152 A292983

Adjacent sequences: A011863 A011864 A011865 * A011867 A011868 A011869

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved