A283894 Relative of Hofstadter Q-sequence: a(1) = 17, a(2) = 2; thereafter a(n) = a(n-a(n-1)) + a(n-a(n-2)).

17, 2, 17, 2, 17, 2, 17, 2, 17, 2, 17, 2, 17, 2, 17, 2, 17, 19, 2, 36, 2, 36, 2, 36, 2, 36, 2, 36, 2, 36, 2, 36, 2, 36, 2, 36, 19, 4, 38, 38, 34, 4, 55, 38, 17, 4, 91, 38, 17, 4, 127, 38, 17, 21, 40, 4, 34, 57, 4, 21, 72, 34, 2, 70, 2, 70, 2, 70, 2, 70, 19, 19, 42, 76, 2

Offset: 1

Author

Nathan Fox, Mar 19 2017

Keywords

• nonn

Comments

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

Most terms in this sequence alternate between 2 and a large number. Such runs of terms are separated by 102 other terms, and each run is approximately twice as long as the previous.

Links

• Nathan Fox, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A005185, A278066, A278067, A278068, A283893, A283895, A283896, A283897.

Programs

Maple

A283894:=proc(n) option remember: if n <= 0 then 0: elif n = 1 then 17: elif n = 2 then 2: else A283894(n-A283894(n-1)) + A283894(n-A283894(n-2)): fi: end:

Formula

For nonnegative integers i, if 1 <= 2n + r <= 594*2^(i+1) - 2, then

a(594*2^i + 100 + 2n) = 2

a(594*2^i + 100 + 2n + 1) = 594*2^(i+1) - 2.