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%I #24 Jun 18 2021 02:39:30
%S 20,9,243,1782,14661,118665,962604,7806213,63306927,513404406,
%T 4163593185,33765791949,273832882308,2220722303697,18009552066651,
%U 146053365199830,1184459524998669,9605696961789153,77900014457512092
%N a(0)=20, a(1)=9; for n >= 0, a(n+2) = 7*a(n+1) + 9*a(n).
%C From an online IQ test (Adaptive IQ).
%H G. C. Greubel, <a href="/A136010/b136010.txt">Table of n, a(n) for n = 0..999</a> [Offset shifted by _Georg Fischer_, Jun 18 2021]
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (7,9).
%F G.f.: (20 - 131*x)/(1-7*x-9*x^2). - _M. F. Hasler_, Mar 27 2008
%F a(n) = (10 + 61/sqrt(85))*(7/2 - sqrt(85)/2)^n + (10 - 61/sqrt(85))*(7/2 + sqrt(85)/2)^n. - _Alexander R. Povolotsky_, simplified by _M. F. Hasler_, Mar 29 2008
%p A136010:=n -> simplify((10+61/sqrt(85))*(7/2-1/2*sqrt(85))^n+(10-61/sqrt(85))*(7/2+1/2*sqrt(85))^n); # _M. F. Hasler_, Mar 29 2008
%t LinearRecurrence[{7, 9}, {20, 9}, 50] (* _G. C. Greubel_, Feb 21 2017 *)
%o (PARI) A136010(n) = { local(y=Mod(x,x^2-85)); lift((10+61/y)*(7/2-1/2*y)^n+(10-61/y)*(7/2+1/2*y)^n)} \\ _M. F. Hasler_, improved by _Max Alekseyev_, Mar 29 2008
%o (PARI) my(x='x+O('x^50)); Vec((20 - 131*x)/(1-7*x-9*x^2)) \\ _G. C. Greubel_, Feb 21 2017
%K nonn,easy
%O 0,1
%A Jordan Giedd (jordyg365(AT)gmail.com), Mar 20 2008
%E Definition supplied by _Don Reble_, Mar 27 2008
%E Offset corrected by _Georg Fischer_, Jun 18 2021
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