OFFSET
1,4
COMMENTS
First numbers not occurring: 62, 66, 75, 79, 114, 123, ... .
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Hofstadter's Q-Sequence
Wikipedia, Hofstadter sequence
FORMULA
a(n) = a(n-2 - a(n-2)) + a(n-1 - a(n-3)), with a(1) = a(2) = a(3) = 1.
MATHEMATICA
a[n_]:= a[n]= If[n<4, 1, a[n-2 -a[n-2]] + a[n-1 -a[n-3]]];
Table[a[n], {n, 80}] (* G. C. Greubel, Mar 28 2022 *)
PROG
(Haskell)
a226222 n = a226222_list !! (n-1)
a226222_list = 1 : 1 : 1 : zipWith (+)
(map a226222 $ zipWith (-) [3..] a226222_list)
(map a226222 $ zipWith (-) [2..] $ tail a226222_list)
-- Reinhard Zumkeller, May 31 2013
(Sage)
@CachedFunction
def a(n): # A226222
if (n<4): return 1
else: return a(n-2-a(n-2)) + a(n-1-a(n-3))
[a(n) for n in (1..80)] # G. C. Greubel, Mar 28 2022
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Reinhard Zumkeller, May 31 2013
STATUS
approved