A027619 Numbers k such that Hofstadter Q-sequence Q(k) (A005185) satisfies Q(k) = k/2.

2, 50, 56, 128, 156, 166, 208, 238, 272, 308, 336, 392, 474, 476, 512, 618, 658, 666, 710, 734, 836, 868, 1016, 1064, 1376, 1386, 1424, 1432, 1832, 2216, 2280, 2334, 2606, 2638, 2676, 2700, 2740, 2782, 2786, 2912, 2922, 2948, 2954, 3758

Offset: 1

Author

G. R. Bower (fsgrb(AT)aurora.alaska.edu)

Keywords

• nonn

Programs

Mathematica

q[n_] := q[n] = If[n <= 2, 1, q[n - q[n-1]] + q[n - q[n-2]]];
Reap[For[n = 1, n <= 4000, n++, If[q[n] == n/2, Sow[n]]]][[2, 1]] (* Jean-François Alcover, Oct 02 2019 *)

Formula

Conjecture: a(n)/n^2 is bounded. - Benoit Cloitre, Oct 26 2002