login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

a(n) = floor( n*(n-1)*(n-2)/22 ).
2

%I #24 Oct 18 2024 06:08:35

%S 0,0,0,0,1,2,5,9,15,22,32,45,60,78,99,124,152,185,222,264,310,362,420,

%T 483,552,627,709,797,893,996,1107,1225,1352,1488,1632,1785,1947,2119,

%U 2300,2492,2694,2907,3130,3365,3612,3870,4140,4422,4717,5024,5345,5679,6027,6388,6764,7155,7560,7980,8415,8866,9332,9815,10314,10830,11362,11912,12480,13065,13668

%N a(n) = floor( n*(n-1)*(n-2)/22 ).

%H G. C. Greubel, <a href="/A011904/b011904.txt">Table of n, a(n) for n = 0..2000</a>

%H <a href="/index/Rec#order_14">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1,0,0,0,0,0,0,0,1,-3,3,-1).

%F G.f.: x^4*(1-x+2*x^2-x^3+x^4-x^5+2*x^6-x^8+x^9)/((1-x)^4*(1+x+x^2+x^3+x^4+ x^5+x^6+x^7+x^8+x^9+x^10)). - _Peter J. C. Moses_, Jun 02 2014

%t Table[Floor[(n(n-1)(n-2))/22],{n,0,80}] (* _Harvey P. Dale_, Sep 30 2019 *)

%o (Magma) [Floor(3*Binomial(n,3)/11): n in [0..80]]; // _G. C. Greubel_, Oct 18 2024

%o (SageMath) [3*binomial(n,3)//11 for n in range(81)] # _G. C. Greubel_, Oct 18 2024

%Y Cf. A011886.

%K nonn,easy

%O 0,6

%A _N. J. A. Sloane_

%E More terms added by _G. C. Greubel_, Oct 18 2024