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A283899 Relative of Hofstadter Q-sequence: a(-399) = 400, a(-398) = 4, a(-397) = 400, a(-396) = 4; thereafter a(n) = a(n-a(n-1)) + a(n-a(n-2)). 5

%I

%S 800,4,400,8,800,4,400,12,800,4,400,16,800,4,400,20,800,4,400,24,800,

%T 4,400,28,800,4,400,32,800,4,400,36,800,4,400,40,800,4,400,44,800,4,

%U 400,48,800,4,400,52,800,4,400,56,800,4,400,60

%N Relative of Hofstadter Q-sequence: a(-399) = 400, a(-398) = 4, a(-397) = 400, a(-396) = 4; thereafter a(n) = a(n-a(n-1)) + a(n-a(n-2)).

%C In calculating terms of this sequence, use the convention that a(n)=0 for n<=-400.

%C Sequences like this are more naturally considered with the first nonzero term in position 1. But this sequence would then begin with 400 terms consisting entirely of alternating 4 and 400.

%C This sequence has exactly 465 terms, since a(465)=0 and computing a(466) would refer to itself.

%H Nathan Fox, <a href="/A283899/b283899.txt">Table of n, a(n) for n = 1..465</a>

%p A283899:=proc(n) option remember: if n <= -400 then 0: elif n = -399 then 400: elif n = -398 then 4: elif n = -397 then 400: elif n = -396 then 4: else A283899(n-A283899(n-1)) + A283899(n-A283899(n-2)): fi: end:

%Y Cf. A005185, A283898, A283900, A283901, A283902.

%K nonn,fini,full

%O 1,1

%A _Nathan Fox_, Mar 19 2017

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Last modified January 22 01:28 EST 2022. Contains 350481 sequences. (Running on oeis4.)