A121897 - OEIS

%I #13 Sep 08 2022 08:45:27

%S 1,1,1,1,1,3,11,131,17291,298995971,29799530324409601,

%T 80728364323218860837749108564353,

%U 49748616842002716055120167595193322161740083228987208037683201

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

%H G. C. Greubel, <a href="/A121897/b121897.txt">Table of n, a(n) for n = 1..17</a>

%p a:= proc(n) option remember;

%p       if n<6 then 1

%p     else 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5)

%p       fi;

%p     end:

%p seq(a(n), n=1..15); # _G. C. Greubel_, Oct 07 2019

%t 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 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 (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 (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 (Sage)

%o def a(n):

%o     if (n<6): return 1

%o     else: return 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5)

%o [a(n) for n in (1..15)] # _G. C. Greubel_, Oct 07 2019

%o (GAP)

%o a:= function(n)

%o     if n<6 then return 1;

%o     else return 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5);

%o     fi;

%o   end;

%o List([1..15], n-> a(n) ); # _G. C. Greubel_, Oct 05 2019

%Y Cf. A072879, A121910.

%K nonn

%O 1,6

%A _Roger L. Bagula_, Sep 09 2006

%E Edited by _N. J. A. Sloane_, Sep 15 2006