A140127 - OEIS

%I #16 Aug 01 2021 13:17:03

%S 1,1,1,1,1,-3,5,25,621,385613,148697385121,22110912341822991798377,

%T 488892444587780299304228901641309659922062749,

%U 239015822375015830469277614767879892635108603674971498096787773471947363213442923403867269

%N The first five terms are 1, after that, a(n)=a(n-1)^2-a(n-2)-a(n-3)-a(n-4)-a(n-5).

%e a(7)=5 because (-3)^2-1-1-1-1=5.

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

%p   `if`(n<6, 1, a(n-1)^2 -a(n-2) -a(n-3) -a(n-4) -a(n-5))

%p end:

%p seq(a(n), n=1..14); # _Alois P. Heinz_, Jan 17 2011

%t F[x_] := F[x - 1]^2 - F[x - 2] - F[x - 3] - F[x - 4] - F[x - 5]; F[1] = F[2] = F[3] = F[4] = F[5] = 1

%t RecurrenceTable[{a[1]==a[2]==a[3]==a[4]==a[5]==1,a[n]==a[n-1]^2-a[n-2]-a[n-3]-a[n-4]-a[n-5]},a,{n,15}] (* _Harvey P. Dale_, Aug 01 2021 *)

%K sign

%O 1,6

%A _Ben Branman_, Jun 21 2008

%E More terms from _Alois P. Heinz_, Jan 17 2011