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a(n) = a(n-1)^2 + 2*a(n-2).
2

%I #8 Nov 15 2021 10:41:54

%S 2,3,13,175,30651,939484151,882630469980252103,

%T 779036546537560708779146801314890911,

%U 606897940841168991954208317469740424253072728119076070803668647790914127

%N a(n) = a(n-1)^2 + 2*a(n-2).

%D Found in a Harpers' magazine article on Chinese civil service exam.

%t RecurrenceTable[{a[0]==2,a[1]==3,a[n]==a[n-1]^2+2a[n-2]},a,{n,10}] (* _Harvey P. Dale_, Jun 20 2017 *)

%K nonn

%O 0,1

%A Bob Mckaige (bobmckz(AT)yahoo.com), Jan 20 2006

%E Edited by _Jonathan Vos Post_ and _Joshua Zucker_, Jan 24 2006