A173098 a(1)=1, a(2)=2, a(n)=2*a(n-2)*a(n-1)-a(n-1).

1, 2, 2, 6, 18, 198, 6930, 2737350, 37936933650, 207693292716721350, 15758493330480878908260133650, 6545866736124132578837836330405530973356721350

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Feb 09 2010

Keywords

• nonn

Crossrefs

Cf. A173093, A173094, A173096, A173097

Programs

Mathematica

a=1;b=2;lst={a,b};Do[c=2*a*b-b;AppendTo[lst,c];a=b;b=c,{n,12}];lst
RecurrenceTable[{a[1]==1,a[2]==2,a[n]==2a[n-2]a[n-1]-a[n-1]},a,{n,14}] (* Harvey P. Dale, Jan 27 2012 *)