cp's OEIS Frontend

A373235 Relative of Hofstadter Q-sequence: a(n) = max(0, n+2087) for n <= 0; a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) for n > 0.

%I A373235 #10 Jun 02 2025 15:27:44
%S A373235 6,2088,2089,2090,9,2091,2092,2093,12,2094,2095,2096,15,2097,2098,17,
%T A373235 2100,18,2100,2102,2103,22,21,4185,4179,9,18,4194,4197,2096,22,2117,
%U A373235 2122,2100,27,36,2124,4184,2091,39,2125,2131,2095,42,2127,2134,16,2126,2134,2114,40,2126,55,4198,2103,46,2136,2147,25,38,58,8399,4188
%N A373235 Relative of Hofstadter Q-sequence: a(n) = max(0, n+2087) for n <= 0;  a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) for n > 0.
%C A373235 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 2087 terms.
%C A373235 This sequence has exactly 2341 terms (of positive index).  a(2341) = 0, so an attempt to calculate a(2342) would refer to itself.
%C A373235 Without the convention that a(n) = 0 for n <= -2087, this sequence would have exactly 24 terms (of positive index), since computing a(25) refers to a(-4790).
%C A373235 If 2087 in this sequence's definition is replaced by any larger number congruent to 1 mod 7, the behavior is essentially the same, though the quasilinear part (see Formula section) lasts longer.
%H A373235 Nathan Fox, <a href="/A373235/b373235.txt">Table of n, a(n) for n = 1..2341</a>
%F A373235 If the index is between 67 and 2085 (inclusive), then a(7n) = 7n+2, a(7n+1) = 7n+2089, a(7n+2) = 7n+2091, a(7n+3) = 7, a(7n+4) = 2n+4219, a(7n+5) = n+4167, a(7n+6) = 2085.
%Y A373235 Cf. A005185, A267501, A278055, A373234, A373236, A373237, A373238, A274058, A373239.
%K A373235 nonn,fini,full
%O A373235 1,1
%A A373235 _Nathan Fox_, May 28 2024