%I #11 Mar 08 2020 18:24:21

%S 1,2,3,4,5,7,10,28,99,1908,136178,246396654,33083692025310,

%T 8147205746460109635768,269537638338486762080764802762484576,

%U 2195978587041305889551144566841383797948181151148527903340

%N a(n) = (a(n-1) + a(n-4)) * (a(n-2) - a(n-3)) with a(1)=1, a(2)=2, a(3)=3 and a(4)=4

%F a(n) = (a(n-1) + a(n-4)) * (a(n-2) - a(n-3)) with a(1)=1, a(2)=2, a(3)=3 and a(4)=4

%F a(n) = k^(phi^n + o(1)) with k = 1.06164666362... and phi = (1+sqrt(5))/2. [_Charles R Greathouse IV_, Jun 21 2011]

%e a(5) = (4+1)*(3-2) = 5 ; a(6) = (5+2)*(4-3) = 7

%t RecurrenceTable[{a[1]==1,a[2]==2,a[3]==3,a[4]==4,a[n]==(a[n-1]+ a[n-4])(a[n-2]- a[n-3])},a,{n,20}] (* _Harvey P. Dale_, Mar 08 2020 *)

%o (PARI) a=vector(20,i,i);for(n=6,#a,a[n]=(a[n-1]+a[n-4])*(a[n-2]-a[n-3]));a \\ _Charles R Greathouse IV_, Jun 21 2011

%K nonn

%O 1,2

%A _Karsten Meyer_, Jun 18 2011