A011895 - OEIS

A011895

a(n) = floor(n*(n-1)*(n-2)/13).

0, 0, 0, 0, 1, 4, 9, 16, 25, 38, 55, 76, 101, 132, 168, 210, 258, 313, 376, 447, 526, 613, 710, 817, 934, 1061, 1200, 1350, 1512, 1686, 1873, 2074, 2289, 2518, 2761, 3020, 3295, 3586, 3893, 4218, 4560, 4920, 5298, 5695, 6112, 6549, 7006, 7483

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OFFSET

0,6

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (3,-3,1,0,0,0,0,0,0,0,0,0,1,-3,3,-1).

FORMULA

a(n) = +3*a(n-1) -3*a(n-2) +a(n-3) +a(n-13) -3*a(n-14) +3*a(n-15) -a(n-16). -R. J. Mathar, Apr 15 2010

G.f.: x^4*(1 +x +2*x^5 +2*x^9 -x^10 +x^11)/((1 -x)^4*(1 +x +x^2 +x^3 +x^4 +x^5 +x^6 +x^7 +x^8 +x^9 +x^10 +x^11 +x^12)). - Colin Barker, Sep 07 2016

PROG

(Magma) [n*(n-1)*(n-2) div 13: n in [0..50]]; // Vincenzo Librandi, Sep 07 2016

(PARI) concat(vector(4), Vec(x^4*(1 +x +2*x^5 +2*x^9 -x^10 +x^11) / ((1 -x)^4*(1 +x +x^2 +x^3 +x^4 +x^5 +x^6 +x^7 +x^8 +x^9 +x^10 +x^11 +x^12)) + O(x^50))) \\ Colin Barker, Sep 07 2016

CROSSREFS

Sequence in context: A181640 A033616 A265055 * A033612 A033610 A019573

Adjacent sequences: A011892 A011893 A011894 * A011896 A011897 A011898

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved