%I #21 Oct 14 2024 11:23:45
%S 1,13,122,1010,7851,58863,431572,3118660,22318901,158673713,
%T 1122923022,7921496310,55755649951,391815428563,2750337394472,
%U 19290508733960,135224296001001,947523746323413,6637434595845922
%N Expansion of 1/((1-x)(1-5x)(1-7x)).
%H John Machacek, <a href="https://arxiv.org/abs/2410.06177">A finite totally nonnegative Grassmannian</a>, arXiv:2410.06177 [math.CO], 2024. See p. 12.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (13,-47,35).
%F a(0)=1, a(1)=13, a(n)=12*a(n-1)-35*a(n-2)+1. - _Vincenzo Librandi_, Feb 10 2011
%F a(n) = (2*7^(n+2) - 3*5^(n+2) + 1)/24. - _Yahia Kahloune_, Aug 13 2013
%p a:=n->sum((7^(n-j)-5^(n-j))/2,j=0..n): seq(a(n), n=1..19); # _Zerinvary Lajos_, Jan 15 2007
%o (PARI) a(n) = (2*7^(n+2) - 3*5^(n+2) + 1)/24; \\ _Joerg Arndt_, Aug 13 2013
%K nonn,easy
%O 0,2
%A _N. J. A. Sloane_