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%I
%S 10,10002,10003,10004,10005,14,10006,10007,10008,10009,18,10010,10011,
%T 10012,10013,22,10014,10015,10016,10017,26,10018,10019,10020,10021,30,
%U 10022,10023,10024,10025,34,10026,10027,10028,37,10030,10030,39
%N Relative of Hofstadter Q-sequence: a(n) = max(0, n+10001) for n <= 0; a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) + a(n-a(n-4)) for n > 0.
%C Sequences like this are more naturally considered with the first nonzero term in position 1. But this sequence would then match A000027 for its first 10001 terms.
%C This sequence has some stretches where it is quasilinear, but it appears to be ultimately chaotic.
%H Nathan Fox, <a href="/A283890/b283890.txt">Table of n, a(n) for n = 1..50000</a>
%p A283890:=proc(n) option remember: if n <= 0 then max(0, n+10001): else A283890(n-A283890(n-1)) + A283890(n-A283890(n-2)) + A283890(n-A283890(n-3)) + A283890(n-A283890(n-4)): fi: end:
%Y Cf. A005185, A283889, A283891, A283892.
%K nonn,look
%O 1,1
%A _Nathan Fox_, Mar 19 2017
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