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A026041 a(n) = d(n)/2, where d = A026040. 1

%I

%S 12,20,32,49,72,102,140,187,244,312,392,485,592,714,852,1007,1180,

%T 1372,1584,1817,2072,2350,2652,2979,3332,3712,4120,4557,5024,5522,

%U 6052,6615,7212,7844,8512,9217,9960,10742,11564,12427,13332,14280,15272,16309,17392,18522,19700,20927,22204,23532,24912,26345

%N a(n) = d(n)/2, where d = A026040.

%H Vincenzo Librandi, <a href="/A026041/b026041.txt">Table of n, a(n) for n = 4..1000</a>

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1).

%F For n>4, a(n) = a(n-1)+A022856(n+2). - Levi R. Self (levi.r.self(AT)gmail.com), Aug 04 2007

%F G.f.: -x^4*(7*x^3-24*x^2+28*x-12)/(x-1)^4. - _Colin Barker_, Oct 07 2012

%F For n>3, a(n) = n*(n^2-3*n+14)/6. - _Vincenzo Librandi_, Oct 17 2013

%t CoefficientList[Series[-(7 x^3 - 24 x^2 + 28 x - 12)/(x - 1)^4, {x, 0, 60}], x] (* _Vincenzo Librandi_, Oct 17 2013 *)

%o (MAGMA) [n*(n^2-3*n+14)/6: n in [4..60]]; // _Vincenzo Librandi_, Oct 17 2013

%K nonn

%O 4,1

%A _Clark Kimberling_

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Last modified June 17 00:17 EDT 2021. Contains 345080 sequences. (Running on oeis4.)