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%I #11 Jul 27 2020 00:18:27
%S 1540,4,770,8,1540,4,770,12,1540,4,770,16,1540,4,770,20,1540,4,770,24,
%T 1540,4,770,28,1540,4,770,32,1540,4,770,36,1540,4,770,40,1540,4,770,
%U 44,1540,4,770,48,1540,4,770,52,1540,4,770,56
%N Relative of Hofstadter Q-sequence: a(-769) = 770, a(-768) = 4, a(-767) = 770, a(-766) = 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<=-770.
%C Sequences like this are more naturally considered with the first nonzero term in position 1. But this sequence would then begin with 770 terms consisting entirely of alternating 4 and 770.
%C This sequence has exactly 8520 terms, since a(8520)=0 and computing a(8521) would refer to itself.
%C a(n) = 2*a(n-4) - a(n-8) for 8 < n <= 770 and for 782 < n <= 1540. a(n) = a(n-4) + a(n-8) - a(n-12) for 1565 < n <= 2310. - _Chai Wah Wu_, Jul 26 2020
%H Nathan Fox, <a href="/A283900/b283900.txt">Table of n, a(n) for n = 1..8520</a>
%p A283900:=proc(n) option remember: if n <= -770 then 0: elif n = -769 then 770: elif n = -768 then 4: elif n = -767 then 770: elif n = -766 then 4: else A283900(n-A283900(n-1)) + A283900(n-A283900(n-2)): fi: end:
%Y Cf. A005185, A283898, A283899, A283901, A283902.
%K nonn,fini,full
%O 1,1
%A _Nathan Fox_, Mar 19 2017
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