cp's OEIS Frontend

A283903 Relative of Hofstadter Q-sequence.

%I A283903 #7 Mar 19 2017 19:26:51
%S A283903 11,20,6,6,6,20,11,20,6,6,6,20,11,6,12,12,12,20,11,6,18,18,12,40,11,
%T A283903 12,24,18,12,40,11,18,30,18,18,40,11,24,30,18,18,80,11,30,30,24,24,80,
%U A283903 11,30,36,30,24,80,11,30,48,24,24,80,11,36,54,24,24,160,11,48,42,36,30,120,11,54,42
%N A283903 Relative of Hofstadter Q-sequence.
%C A283903 This sequence is defined by a(n) = 0 for n <= 0; a(1) = 11, a(2) = 20, a(3) = 6, a(4) = 6, a(5) = 6, a(6) = 20, a(7) = 11, a(8) = 20, a(9) = 6, a(10) = 6, a(11) = 6, a(12) = 20, a(13) = 11, a(14) = 6, a(15) = 12, a(16) = 12, a(17) = 12, a(18) = 20; thereafter a(n) = a(n-a(n-1)) + a(n-a(n-2)).
%C A283903 Similar to Hofstadter's Q-sequence A005185 but with different starting values.
%C A283903 For as long as it exists, this sequence has a similar structure to A272160. That sequence consists of five interleaved sequences: four chaotic sequences and a sequence of all 4's. This sequence consists of six interleaved sequences: five chaotic sequences and a sequence of all 11's.
%C A283903 If the 20's in the initial condition are each replaced by larger numbers, the general structure of this sequence does not change.
%C A283903 This sequence has exactly 2179 terms, since a(2179)=0 and computing a(2180) would refer to itself.
%H A283903 Nathan Fox, <a href="/A283903/b283903.txt">Table of n, a(n) for n = 1..2179</a>
%p A283903 A283903:=proc(n) option remember: if n <= 0 then 0: elif n = 1 then 11: elif n = 2 then 20: elif n = 3 then 6: elif n = 4 then 6: elif n = 5 then 6: elif n = 6 then 20: elif n = 7 then 11: elif n = 8 then 20: elif n = 9 then 6: elif n = 10 then 6: elif n = 11 then 6: elif n = 12 then 20: elif n = 13 then 11: elif n = 14 then 6: elif n = 15 then 12: elif n = 16 then 12: elif n = 17 then 12: elif n = 18 then 20: else A283903(n-A283903(n-1)) + A283903(n-A283903(n-2)): fi: end:
%Y A283903 Cf. A005185, A272610, A284053, A284054.
%K A283903 nonn,fini,full
%O A283903 1,1
%A A283903 _Nathan Fox_, Mar 19 2017