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

1, 1, 1, 1, 1, 3, 11, 131, 17291, 298995971, 29799530324409601, 80728364323218860837749108564353, 49748616842002716055120167595193322161740083228987208037683201

Offset: 1

Author

Roger L. Bagula, Sep 09 2006

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..17

Crossrefs

Cf. A072879, A121910.

Programs

GAP

a:= function(n)
    if n<6 then return 1;
    else return 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5);
    fi;
  end;
List([1..15], n-> a(n) ); # G. C. Greubel, Oct 05 2019

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

Maple

a:= proc(n) option remember;
      if n<6 then 1
    else 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5)
      fi;
    end:
seq(a(n), n=1..15); # G. C. Greubel, Oct 07 2019

Mathematica

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}]
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 *)

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

Sage

def a(n):
    if (n<6): return 1
    else: return 4*a(n-1)*a(n-2)*a(n-3)*a(n-4) - a(n-5)
[a(n) for n in (1..15)] # G. C. Greubel, Oct 07 2019

Extensions

Edited by N. J. A. Sloane, Sep 15 2006