A063401 a(n) = a(n-1)*a(n-2)*a(n-3) with a(0)=1, a(1)=2, a(2)=2.

1, 2, 2, 4, 16, 128, 8192, 16777216, 17592186044416, 2417851639229258349412352, 713623846352979940529142984724747568191373312, 30354201441027016733116592294117482916287606860189680019559568902170379456331382784

Offset: 0

Author

Henry Bottomley, Jul 16 2001

Keywords

• nonn

Examples

			a(6) = 128*16*4 = 8192.
		

Links

• Harry J. Smith, Table of n, a(n) for n=0,...,15

Crossrefs

Cf. A000301, A000308.

Programs

Mathematica

a0=1;a1=1;a2=2;lst={a0,a1,a2};Do[AppendTo[lst,a=a0*a1*a2]; a0=a1;a1=a2;a2=a, {n,12}];lst (* Vladimir Joseph Stephan Orlovsky, Nov 18 2009 *)
RecurrenceTable[{a[0]==1,a[1]==a[2]==2,a[n]==a[n-1]a[n-2]a[n-3]},a,{n,12}] (* Harvey P. Dale, Sep 05 2021 *)

PARI

{ for (n = 0, 15, if (n>2, a=a1*a2*a3; a3=a2; a2=a1; a1=a, if (n==0, a=a3=1; a1=a2=2, a=2)); write("b063401.txt", n, " ", a) ) } \\ Harry J. Smith, Aug 20 2009

Formula

a(n) = 2^A000073(n+1).

Extensions

Definition corrected to a(1)=2 by Harry J. Smith, Aug 20 2009