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A100451 a(n) = 0 for n <= 2; for n >= 3, a(n) = (n-2)*floor((n^2-2)/(n-2)).

%I A100451 #35 Feb 01 2025 23:19:56
%S A100451 0,0,7,14,21,32,45,60,77,96,117,140,165,192,221,252,285,320,357,396,
%T A100451 437,480,525,572,621,672,725,780,837,896,957,1020,1085,1152,1221,1292,
%U A100451 1365,1440,1517,1596,1677,1760,1845,1932,2021,2112,2205,2300,2397,2496,2597,2700
%N A100451 a(n) = 0 for n <= 2; for n >= 3, a(n) = (n-2)*floor((n^2-2)/(n-2)).
%H A100451 Vincenzo Librandi, <a href="/A100451/b100451.txt">Table of n, a(n) for n = 1..10000</a>
%H A100451 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A100451 a(n) = (n-2)*(n+2), n >= 5. - _R. J. Mathar_, Aug 17 2009
%F A100451 a(n) = A028347(n), n >= 5. - _R. J. Mathar_, Jul 31 2010
%t A100451 Join[{0,0,7,14},Table[(n-2)(n+2),{n,5,60}]] (* or *) Join[{0,0,7,14}, LinearRecurrence[{3,-3,1},{21,32,45},60]] (* _Harvey P. Dale_, Oct 03 2011 *)
%o A100451 (Magma) [0, 0] cat [(n-2)*Floor((n^2-2)/(n-2)): n in [3..30]]; // _Vincenzo Librandi_, Oct 04 2011
%o A100451 (PARI) a(n)=if(n<3,0,(n^2-2)\(n-2)*(n-2)) \\ _Charles R Greathouse IV_, Oct 16 2015
%o A100451 (SageMath)
%o A100451 def A100451(n):
%o A100451     return 7 * (n - 2) * ((n - 1) // 2) if n < 5 else (n - 2) * (n + 2)
%o A100451 print([A100451(n) for n in range(1, 61)])  # _G. C. Greubel_, Apr 07 2023
%Y A100451 Third row of array in A100452.
%Y A100451 Cf. A028347.
%K A100451 nonn,easy
%O A100451 1,3
%A A100451 _N. J. A. Sloane_, Nov 22 2004
%E A100451 Factor in definition corrected by _R. J. Mathar_, Aug 17 2009