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!)
A324665 Starting at n, a(n) is the total number of negative positions visited according to the following rules. On the k-th step (k=1,2,3,...) 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. 2
0, 0, 2, 0, 17, 17, 0, 939, 6, 6, 0, 8, 73, 73, 7, 0, 48, 445544, 10, 10, 57947, 0, 30, 16, 16, 782680, 11, 11, 0, 184, 2650008, 232081, 232079, 232079, 232079, 12, 0, 35, 109811, 109809, 123, 17, 15, 15, 577, 0, 82, 62, 62, 45, 45, 104, 32, 16, 16, 0, 281, 279 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..57.

David Nacin, A324665(n)/A228474(n)

EXAMPLE

For n=2, the points visited are 2,1,-1,-4,0.  As exactly two of these are negative, we have a(2)=2.

PROG

(Python)

#Sequences A324660-A324692 generated by manipulating this trip function

#spots - positions in order with possible repetition

#flee - positions from which we move away from zero with possible repetition

#stuck - positions from which we move to a spot already visited with possible repetition

def trip(n):

    stucklist = list()

    spotsvisited = [n]

    leavingspots = list()

    turn = 0

    forbidden = {n}

    while n != 0:

        turn += 1

        sign = n // abs(n)

        st = sign * turn

        if n - st not in forbidden:

            n = n - st

        else:

            leavingspots.append(n)

            if n + st in forbidden:

                stucklist.append(n)

            n = n + st

        spotsvisited.append(n)

        forbidden.add(n)

    return {'stuck':stucklist, 'spots':spotsvisited,

                'turns':turn, 'flee':leavingspots}

#Actual sequence

def a(n):

    d = trip(n)

    return sum(1 for i in d['spots'] if i < 0)

CROSSREFS

Cf. A228474, A324660-A324692

Sequence in context: A178987 A242569 A152154 * A261516 A009198 A209123

Adjacent sequences:  A324662 A324663 A324664 * A324666 A324667 A324668

KEYWORD

nonn

AUTHOR

David Nacin, Mar 10 2019

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 September 19 03:31 EDT 2021. Contains 347550 sequences. (Running on oeis4.)