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A121897 a(n) = 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5).

%I A121897 #13 Sep 08 2022 08:45:27
%S A121897 1,1,1,1,1,3,11,131,17291,298995971,29799530324409601,
%T A121897 80728364323218860837749108564353,
%U A121897 49748616842002716055120167595193322161740083228987208037683201
%N A121897 a(n) = 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5).
%H A121897 G. C. Greubel, <a href="/A121897/b121897.txt">Table of n, a(n) for n = 1..17</a>
%p A121897 a:= proc(n) option remember;
%p A121897       if n<6 then 1
%p A121897     else 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5)
%p A121897       fi;
%p A121897     end:
%p A121897 seq(a(n), n=1..15); # _G. C. Greubel_, Oct 07 2019
%t A121897 a[n_]:= a[n]= If[n<6, 1, 4*a[n-1]*a[n-2]*a[n-3]*a[n-4] - a[n-5]];  Table[a[n], {n, 15}]
%t A121897 RecurrenceTable[{a[1]==a[2]==a[3]==a[4]==a[5]==1,a[n]==4a[n-1]a[n-2]a[n-3]a[n-4]-a[n-5]},a,{n,15}] (* _Harvey P. Dale_, Dec 16 2018 *)
%o A121897 (PARI) my(m=15, v=concat([1,1,1,1,1], vector(m-5))); for(n=6, m, v[n] = 4*v[n-1]*v[n-2]*v[n-3]*v[n-4] - v[n-5]); v \\ _G. C. Greubel_, Oct 07 2019
%o A121897 (Magma) [n lt 6 select 1 else 4*Self(n-1)*Self(n-2)*Self(n-3)*Self(n-4) - Self(n-5): n in [1..15]]; // _G. C. Greubel_, Oct 07 2019
%o A121897 (Sage)
%o A121897 def a(n):
%o A121897     if (n<6): return 1
%o A121897     else: return 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5)
%o A121897 [a(n) for n in (1..15)] # _G. C. Greubel_, Oct 07 2019
%o A121897 (GAP)
%o A121897 a:= function(n)
%o A121897     if n<6 then return 1;
%o A121897     else return 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5);
%o A121897     fi;
%o A121897   end;
%o A121897 List([1..15], n-> a(n) ); # _G. C. Greubel_, Oct 05 2019
%Y A121897 Cf. A072879, A121910.
%K A121897 nonn
%O A121897 1,6
%A A121897 _Roger L. Bagula_, Sep 09 2006
%E A121897 Edited by _N. J. A. Sloane_, Sep 15 2006