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%I #14 Oct 16 2020 15:28:42
%S 0,1,2,2,4,8,16,48,176,944,9392,175536,9041584,1657675696,
%T 1588781164720,14989602831307184,2633698912621747952304,
%U 23815201278713350097371300784,39478100701260806183512640492975852720
%N a(0)=0; a(1)=1; a(2)=2; a(n)= a(n-1) + a(n-2)*a(n-3).
%H Harry J. Smith, <a href="/A063402/b063402.txt"> Table of n, a(n) for n = 0..29</a>
%t nxt[{a_,b_,c_}]:={b,c,c+a*b}; NestList[nxt,{0,1,2},20][[All,1]] (* _Harvey P. Dale_, Oct 16 2020 *)
%o (PARI) { for (n = 0, 29, if (n>2, a=a1 + a2*a3; a3=a2; a2=a1; a1=a, if (n==0, a=a3=0; a2=1; a1=2, if (n==1, a=1, a=2))); write("b063402.txt", n, " ", a) ) } \\ _Harry J. Smith_, Aug 20 2009
%Y Cf. A006888.
%K nonn,easy
%O 0,3
%A _Olivier Gérard_, Jul 16 2001
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