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A188670
A quasi-periodic solution to Hofstadter's Q recurrence.
16
3, 6, 5, 3, 6, 8, 3, 6, 13, 3, 6, 21, 3, 6, 34, 3, 6, 55, 3, 6, 89, 3, 6, 144, 3, 6, 233, 3, 6, 377, 3, 6, 610, 3, 6, 987, 3, 6, 1597, 3, 6, 2584, 3, 6, 4181, 3, 6, 6765, 3, 6, 10946, 3, 6, 17711, 3, 6, 28657, 3, 6, 46368, 3, 6, 75025, 3, 6, 121393
OFFSET
0,1
COMMENTS
a(n) is the solution to the recurrence relation a(n) = a(n-a(n-1)) +a(n-a(n-2)) [Hofstadter's Q recurrence], with the initial conditions: a(n) = 0 if n < 0; a(n) = 3 if n = 0,3; a(n) = 6 if n = 1,4; a(2) = 5; a(5) = 8.
REFERENCES
F. Ruskey, Fibonacci meets Hofstadter, Fibonacci Quart. 49 (2011), no. 3, 227-230.
LINKS
Nathan Fox, Linear-Recurrent Solutions to Meta-Fibonacci Recurrences, Part 1 (video), Rutgers Experimental Math Seminar, Oct 01 2015. Part 2 is vimeo.com/141111991.
FORMULA
a(3n) = 3, a(3n+1) = 6, a(3n+2) = Fibonacci(n+5).
From Colin Barker, Nov 23 2015: (Start)
a(n) = 2*a(n-3)-a(n-9) for n>8.
G.f.: -(3*x^8+6*x^7+3*x^6+2*x^5+6*x^4+3*x^3-5*x^2-6*x-3) / ((x-1)*(x^2+x+1)*(x^6+x^3-1)).
(End)
PROG
(PARI)
{
local(m=n%3);
if (m==0, return(3));
if (m==1, return(6));
return(fibonacci(n\3+5));
}
vector(66, n, A188670(n-1)) /* show terms */ /* Joerg Arndt, Apr 08 2011 */
(PARI) Vec(-(3*x^8+6*x^7+3*x^6+2*x^5+6*x^4+3*x^3-5*x^2-6*x-3)/((x-1)*(x^2+x+1)*(x^6+x^3-1)) + O(x^100)) \\ Colin Barker, Nov 23 2015
CROSSREFS
Cf. A005185 with different initial conditions.
Sequence in context: A019652 A099874 A011223 * A361985 A346602 A102621
KEYWORD
nonn,easy
AUTHOR
Frank Ruskey, Apr 08 2011
STATUS
approved