A373238 Relative of Hofstadter Q-sequence: a(n) = max(0, n+200) for n <= 0; a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) for n > 0.

6, 201, 202, 203, 9, 204, 205, 206, 12, 207, 208, 209, 15, 210, 211, 17, 213, 18, 213, 215, 216, 22, 21, 411, 405, 9, 18, 420, 423, 209, 22, 230, 235, 213, 27, 36, 237, 410, 204, 39, 238, 244, 208, 42, 240, 247, 16, 239, 247, 227, 40, 239, 55, 424, 216, 46, 249, 260, 25, 38, 58, 851, 414, 204, 61, 71, 463, 402, 198, 72, 272, 274

Offset: 1

Author

Nathan Fox, May 28 2024

Keywords

• nonn
• fini
• full

Comments

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 200 terms.

This sequence has exactly 220 terms (of positive index). a(220) = 0, so an attempt to calculate a(221) would refer to itself.

Without the convention that a(n) = 0 for n <= -200, this sequence would have exactly 24 terms (of positive index), since computing a(25) refers to a(-386).

If 200 in this sequence's definition is replaced by any larger number congruent to 4 mod 7, the behavior is essentially the same, though the quasilinear part (see Formula section) lasts longer.

Links

• Nathan Fox, Table of n, a(n) for n = 1..220

Crossrefs

Cf. A005185, A267501, A278055, A373234, A373235, A373236, A373237, A274058, A373239.

Formula

If the index is between 67 and 202 (inclusive), then a(7n) = 7n+2, a(7n+1) = 7n+202, a(7n+2) = 7n+204, a(7n+3) = 7, a(7n+4) = 2n+445, a(7n+5) = n+393, a(7n+6) = 198.