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A064657 a(n) = a(|n - a(n-3)|) + a(|n - a(n-4)|) for n > 3, a(n)=1 otherwise.

%I A064657 #28 Jul 03 2025 17:44:01
%S A064657 1,1,1,1,2,4,8,12,10,5,2,2,13,12,26,13,3,9,14,11,11,25,12,26,13,13,27,
%T A064657 27,26,4,2,6,34,10,60,5,28,53,22,62,25,24,22,25,22,51,38,25,28,3,26,
%U A064657 53,16,53,27,63,26,4,10,12,86,57,42,79,24,36,25,38,56,32,85,23
%N A064657 a(n) = a(|n - a(n-3)|) + a(|n - a(n-4)|) for n > 3, a(n)=1 otherwise.
%C A064657 The sequence is defined only for n <= 866, see example. - _Reinhard Zumkeller_, Jul 21 2012
%H A064657 Reinhard Zumkeller, <a href="/A064657/b064657.txt">full Table of n, a(n) for n = 0..866</a>
%e A064657 Last term: a(866) = a(|866 - a(866-3)|) + a(|866 - a(866-4)|) = a(|866 - a(863)|) + a(|866 - a(862)|) = a(|866 - 718|) + a(|866 - 88|) = a(148) + a(778) = 28 + 655 = 683,
%e A064657 but a(867) = a(|867 - a(867-3)|) + a(|867 - a(867-4)|) = a(|867 - a(864)|) + a(|867 - a(863)|) =  a(|867 - 2546|) + a(|867 - 718|) = a(1679) + a(149) = undefined + 112 = undefined.
%o A064657 (Haskell)
%o A064657 a064657 n = a064657_list !! n
%o A064657 a064657_list = map fromJust $ takeWhile (/= Nothing) zs where
%o A064657   z n = fromJust $ zs !! n
%o A064657   zs = (map Just [1,1,1,1]) ++ f 4 where
%o A064657      f x = y : f (x + 1) where
%o A064657        y | 2*x < max i3 i4 = Nothing
%o A064657          | otherwise       = Just $ z (abs (x - i3)) + z (abs (x - i4))
%o A064657          where i3 = z (x - 3); i4 = z (x - 4)
%o A064657 b064657 = bFile' "A064657" a064657_list 0 -- (0.03 secs, 3184228 bytes)
%o A064657 -- _Reinhard Zumkeller_, Jul 21 2012
%o A064657 (PARI) A064657_vec=[1,1,1]; A064657(n)={n<4 & return(1);
%o A064657 #A064657_vec<n & A064657_vec=concat(A064657_vec, vector(n-#A064657_vec)); A064657_vec[n] & return(A064657_vec[n]); A064657_vec[n]=A064657(abs(A064657(n-3)-n))+A064657(abs(A064657(n-4)-n))} \\ - _M. F. Hasler_, Aug 28 2012
%K A064657 nonn,fini,full
%O A064657 0,5
%A A064657 _Roger L. Bagula_, Oct 08 2001
%E A064657 More terms from _Vladeta Jovovic_, Oct 09 2001
%E A064657 Keyword fini added by _Reinhard Zumkeller_, Jul 21 2012