%I #22 Sep 08 2022 08:45:28
%S 7,13,8,12,9,11,10,10,11,9,12,8,13,7,14,6,15,5,16,4,17,3,18,2,19,1,20,
%T 0,21,-1,22,-2,23,-3,24,-4,25,-5,26,-6,27,-7,28,-8,29,-9,30,-10,31,
%U -11,32,-12,33,-13,34,-14,35,-15,36,-16,37,-17,38,-18,39,-19,40,-20,41,-21,42
%N List of pairs n+7, 13-n, n >= 0.
%H Vincenzo Librandi, <a href="/A122874/b122874.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-1,1,1).
%F a(n) = -a(n-1)+a(n-2)+a(n-3). G.f.: -(7+20*x+14*x^2)/((x-1)*(1+x)^2). [_R. J. Mathar_, Aug 07 2009]
%t CoefficientList[Series[-(7 + 20 x + 14 x^2)/((x - 1) (1 + x)^2), {x, 0, 100}], x] (* _Vincenzo Librandi_, May 25 2014 *)
%o (Magma) &cat[[n+7, 13-n]: n in [0..30]]; // _Vincenzo Librandi_, May 25 2014
%K sign,tabf,easy
%O 0,1
%A Stuart M. Ellerstein (ellerstein(AT)aol.com), Oct 23 2006
%E Edited with better definition by _Omar E. Pol_ and _N. J. A. Sloane_, Jan 02 2009
%E More terms from _R. J. Mathar_, Aug 07 2009