A191864 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.

1, 2, 3, 4, 5, 7, 10, 28, 99, 1908, 136178, 246396654, 33083692025310, 8147205746460109635768, 269537638338486762080764802762484576, 2195978587041305889551144566841383797948181151148527903340

Offset: 1

Author

Karsten Meyer, Jun 18 2011

Keywords

• nonn

Examples

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

Programs

Mathematica

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 *)

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

Formula

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

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