login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A240808 a(0)=2, a(1)=1, a(2)=0; thereafter a(n) = a(n-1-a(n-1))+a(n-2-a(n-2)) unless a(n-1) <= n-1 or a(n-2) <= n-2 in which case the sequence terminates. 8
2, 1, 0, 2, 1, 3, 2, 1, 3, 5, 4, 3, 5, 4, 6, 8, 4, 6, 8, 7, 9, 8, 7, 12, 11, 7, 12, 14, 10, 12, 14, 10, 12, 17, 13, 12, 20, 16, 12, 20, 19, 15, 20, 19, 18, 23, 19, 21, 26, 19, 21, 26, 19, 24, 29, 19, 27, 32, 19, 27, 32, 22, 30, 32, 22, 30, 32, 25, 33, 32, 28, 36, 32, 31, 39, 32, 31, 42, 35, 31, 45, 38, 31, 45, 38, 31, 48, 41, 31, 51, 44, 31, 51, 47, 34 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(A241218(n)) = n and a(m) <> n for m < A241218(n). - Reinhard Zumkeller, Apr 17 2014

REFERENCES

Higham, Jeff and Tanny, Stephen, A tamely chaotic meta-Fibonacci sequence. Twenty-third Manitoba Conference on Numerical Mathematics and Computing (Winnipeg, MB, 1993). Congr. Numer. 99 (1994), 67-94. [Contains a detailed analysis of this sequence]

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..20000

Rémy Sigrist, Colored scatterplot of a(n) for n = 0..20000 (where the color is function of n mod 3)

Index entries for Hofstadter-type sequences

MAPLE

a:=proc(n) option remember; global k;

if n = 0 then 2

elif n = 1 then 1

elif n = 2 then 0

else

if (a(n-1) <= n-1) and (a(n-2) <= n-2) then

a(n-1-a(n-1))+a(n-2-a(n-2));

else lprint("died with n =", n); return (-1);

fi;

fi; end;

[seq(a(n), n=0..100)];

PROG

(Haskell)

a240808 n = a240808_list !! n

a240808_list = 2 : 1 : 0 : zipWith (+) xs (tail xs)

   where xs = map a240808 $ zipWith (-) [1..] $ tail a240808_list

-- Reinhard Zumkeller, Apr 17 2014

CROSSREFS

A006949 and A240807 have the same recurrence but different initial conditions.

Trisections: A244780..A244782.

Sequence in context: A153247 A071432 A194508 * A263142 A025253 A281228

Adjacent sequences:  A240805 A240806 A240807 * A240809 A240810 A240811

KEYWORD

nonn,look

AUTHOR

N. J. A. Sloane, Apr 15 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 23 04:58 EDT 2021. Contains 343199 sequences. (Running on oeis4.)