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A Per Bak sand pile collapse sequence using Hofstadter Q:A005185, of the A153112 form.
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%I #10 Mar 11 2022 08:02:32

%S 1,1,1,2,3,3,4,5,5,6,6,6,8,8,8,10,9,10,1,7,15,12,11,14,14,12,16,16,16,

%T 16,16,20,17,17,20,11,21,25,18,20,26,22,24,19,27,17,23,30,13,28,36,24,

%U 25,32,27,30,32,28,32,36,30,32,3,50,40,22,43,31,37,35,28,40,44,33,38,49

%N A Per Bak sand pile collapse sequence using Hofstadter Q:A005185, of the A153112 form.

%t f[0] = 1; f[1] = 1; f[2] = 1;

%t f[n_] := f[n] = If[Mod[Floor[Sum[f[i], {i, 0, n - 1}]/2], 2^(4 + Mod[n, 3])] == 0, 1 + Mod[n, 3], f[n - f[n - 1]] + f[n - f[n - 2]]];

%t a = Table[f[n], {n, 0, 200}]

%Y Cf. A153112, A005185.

%K nonn,uned

%O 0,4

%A _Roger L. Bagula_, Oct 15 2009