%I #15 May 04 2017 05:06:47
%S 1,2,2,2,3,3,3,5,5,5,5,5,5,7,7,7,8,8,8,8,8,8,10,10,10,13,12,13,13,12,
%T 13,13,13,13,13,13,15,15,15,20,17,20,20,17,20,18,20,20,21,21,20,21,21,
%U 21,21,21,21,21,23,23,23,28,23,28,29,23,32,28,23,31,27,28,33,33,32
%N a(1) = 1, a(2) = a(3) = a(4) = 2; a(n) = a(a(n-3)-1) + a(n-a(n-4)-1) for n > 4.
%H Altug Alkan, <a href="/A285582/b285582.txt">Table of n, a(n) for n = 1..10000</a>
%H Altug Alkan, <a href="/A285582/a285582.png">Alternative scatterplot</a>
%t a[1] = 1; a[2] = a[3] = a[4] = 2; a[n_] := a[n] = a[a[n - 3] - 1] + a[n - a[n - 4] - 1]; Array[a, 75] (* _Michael De Vlieger_, Apr 23 2017 *)
%o (PARI) q=vector(10000); q[1]=1;q[2]=q[3]=q[4]=2; for(n=5, #q, q[n]=q[q[n-3]-1]+q[n-q[n-4]-1]); vector(10000, n, q[n])
%Y Cf. A005185, A055748, A284523
%K nonn,look
%O 1,2
%A _Altug Alkan_, Apr 22 2017
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