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A121910 a(n) = 3*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5), with a(1)=a(2)=a(3)=a(4)=a(5)=1.

%I A121910 #26 Sep 08 2022 08:45:27
%S A121910 1,1,1,1,1,2,5,29,869,756029,285790302433,16335219393063437264866,
%T A121910 9201358366190200404401435237110861938769705
%N A121910 a(n) = 3*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5), with a(1)=a(2)=a(3)=a(4)=a(5)=1.
%H A121910 G. C. Greubel, <a href="/A121910/b121910.txt">Table of n, a(n) for n = 1..17</a>
%p A121910 a:= proc(n) option remember;
%p A121910       if n<6 then 1 else 3*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5) fi;
%p A121910     end:
%p A121910 seq(a(n), n=1..15); # _G. C. Greubel_, Oct 07 2019
%t A121910 a[n_]:= a[n]= If[n<6, 1, 3*a[n-1]*a[n-2]*a[n-3]*a[n-4] - a[n-5]]; Table[a[n], {n, 15}] (* modified by _G. C. Greubel_, Oct 07 2019 *)
%o A121910 (PARI) my(m=15, v=concat([1,1,1,1,1], vector(m-5))); for(n=6, m, v[n] = 3*v[n-1] *v[n-2]*v[n-3]*v[n-4] - v[n-5]); v \\ _G. C. Greubel_, Oct 07 2019
%o A121910 (Magma) [n lt 6 select 1 else 3*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 A121910 (Sage)
%o A121910 def a(n):
%o A121910     if (n<6): return 1
%o A121910     else: return 3*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5)
%o A121910 [a(n) for n in (1..15)] # _G. C. Greubel_, Oct 07 2019
%o A121910 (GAP)
%o A121910 a:= function(n)
%o A121910     if n<6 then return 1;
%o A121910     else return 3*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5);
%o A121910     fi;
%o A121910   end;
%o A121910 List([1..15], n-> a(n) ); # _G. C. Greubel_, Oct 05 2019
%Y A121910 Cf. A072879, A121897.
%K A121910 nonn
%O A121910 1,6
%A A121910 _Roger L. Bagula_, Sep 09 2006
%E A121910 Edited by _N. J. A. Sloane_, Sep 15 2006
%E A121910 Definition adapted to offset by _Georg Fischer_, Jun 18 2021