A107706 - OEIS

%I #5 Jan 19 2015 15:37:13

%S 1,1,3,19,725,1051269,2210333021447,9771144131398048324998887,

%T 190950515273109040540985906104397627141067435498985,

%U 72924198566131697919005645563941249133599421947333610081098812005030529313728193495031984760197059337

%N Quadratic recurrence a(n)=2a(n-1)^2+a(n-2), a(0)=a(1)=1.

%F a(n) ~ 1/2 * c^(2^n), where c = 1.5761071725603835806427292143532632951057735784139134374711... . - _Vaclav Kotesovec_, Jan 19 2015

%t RecurrenceTable[{a[n]==2*a[n-1]^2+a[n-2],a[0]==1,a[1]==1},a,{n,0,10}] (* _Vaclav Kotesovec_, Jan 19 2015 *)

%o (PARI) a(n)=if(n<0, -a(-1-n), if(n<2, 1, 2*a(n-1)^2+a(n-2)))

%K nonn

%O 0,3

%A _Michael Somos_, May 22 2005