This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A285582 #15 May 04 2017 05:06:47 %S A285582 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 A285582 13,13,13,13,13,13,15,15,15,20,17,20,20,17,20,18,20,20,21,21,20,21,21, %U A285582 21,21,21,21,21,23,23,23,28,23,28,29,23,32,28,23,31,27,28,33,33,32 %N A285582 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 A285582 Altug Alkan, <a href="/A285582/b285582.txt">Table of n, a(n) for n = 1..10000</a> %H A285582 Altug Alkan, <a href="/A285582/a285582.png">Alternative scatterplot</a> %t A285582 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 A285582 (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 A285582 Cf. A005185, A055748, A284523 %K A285582 nonn,look %O A285582 1,2 %A A285582 _Altug Alkan_, Apr 22 2017