login
This site is supported by donations to The OEIS Foundation.

 

Logo

The October issue of the Notices of the Amer. Math. Soc. has an article about the OEIS.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A228474 This is a Recamán-like sequence (cf. A005132). Starting at n, a(n) is the number of steps required to reach zero. On the k-th step move a distance of k in the direction of zero. If the number landed on has been landed on before, move a distance of k away from zero instead. 9

%I

%S 0,1,4,2,24,26,3,1725,12,14,4,26,123,125,15,5,119,781802,20,22,132896,

%T 6,51,29,31,1220793,23,25,7,429,8869123,532009,532007,532009,532011,

%U 26,8,94,213355,213353,248,33,31,33,1000,9,144,110,112,82,84,210,60,34

%N This is a Recamán-like sequence (cf. A005132). Starting at n, a(n) is the number of steps required to reach zero. On the k-th step move a distance of k in the direction of zero. If the number landed on has been landed on before, move a distance of k away from zero instead.

%C The n-th triangular number A000217(n) has a(A000217(n)) = n.

%C a(n) + 1 = length of row n in tables A248939 and A248973. - _Reinhard Zumkeller_, Oct 20 2014

%H Jon E. Schoenfield, <a href="/A228474/b228474.txt">Table of n, a(n) for n = 0..10000</a>

%H Gordon Hamilton, <a href="http://www.youtube.com/watch?v=mQdNaofLqVc&amp;feature=youtu.be">Wrecker Ball Sequences</a>, Video, 2013

%H <a href="/index/Rea#Recaman">Index entries for sequences related to Recamán's sequence</a>

%e a(2) = 4 because 2 -> 1 -> -1 -> -4 -> 0.

%o (PARI) a(n)={my(M=Map(),k=0); while(n, k++; mapput(M,n,1); my(t=if(n>0, -k, +k)); n+=if(mapisdefined(M,n+t),-t,t)); k} \\ _Charles R Greathouse IV_, Aug 18 2014, revised _Andrew Howroyd_, Feb 28 2018

%o (Haskell)

%o a228474 = subtract 1 . length . a248939_row -- _Reinhard Zumkeller_, Oct 20 2014

%Y Cf. A000217, A005132.

%Y Cf. A248939, A248973.

%K walk,nonn

%O 0,3

%A _Gordon Hamilton_, Aug 23 2013

%E More terms from _Jon E. Schoenfield_, Jan 10 2014

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 23 05:43 EDT 2018. Contains 315273 sequences. (Running on oeis4.)