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

1,2

Links

Table of n, a(n) for n=1..16.

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]

Example

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

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 *)

Prog

(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

Crossrefs

Sequence in context: A130080 A057496 A345663 * A180348 A001729 A001087

Adjacent sequences: A191861 A191862 A191863 * A191865 A191866 A191867

Keyword

nonn

Author

Karsten Meyer, Jun 18 2011

Status

approved