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A248952 Smallest terms in wrecker ball sequences starting with n. 8
0, 0, -4, 0, -47, -46, 0, -6362, -23, -22, 0, -32, -471, -470, -29, 0, -218, -4843985, -39, -38, -657367, 0, -101, -57, -56, -7609937, -45, -44, 0, -736, -56168428, -3113136, -3113135, -3113134, -3113133, -51, 0, -190, -1213998, -1213997, -495, -62, -61, -60 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n) = smallest term in row n of triangle A248939;

a(A000217(n)) = 0; a(A014132(n)) < 0.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..1000

Gordon Hamilton, Wrecker Ball Sequences, Video, 2013

EXAMPLE

a(0) = min{0} = 0;

a(1) = min{1,0} = 0;

a(2) = min{2,1,-1,-4,0} = -4;

a(3) = min{3,2,0} = 0;

a(4) = min{4,3,1,-2,2,-3,-9,-16,-8,-17,-7,-18,-6,7,21,6,-10,-27,...} = -47;

a(5) = min{5,4,2,-1,3,-2,-8,-15,-7,-16,-6,-17,-5,8,22,7,-9,-26,...} = -46;

a(6) = min{6,5,3,0} = 0;

a(7) = min{7,6,4,1,-3,2,-4,3,-5,-14,-24,-13,-1,12,-2,13,29,46,...} = -6362;

a(8) = min{8,7,5,2,-2,3,-3,4,-4,-13,-23,-12,0} = -23;

a(9) = min{9,8,6,3,-1,4,-2,5,-3,-12,-22,-11,1,14,0} = -22.

PROG

(Haskell)

import Data.IntSet (singleton, member, insert, findMin, findMax)

a248952 n = a248952_list !! n

(a248952_list, a248953_list) = unzip $

   map (\x -> minmax 1 x $ singleton x) [0..] where

   minmax _ 0 s = (findMin s, findMax s)

   minmax k x s = minmax (k + 1) y (insert y s) where

                         y = x + (if (x - j) `member` s then j else -j)

                         j = k * signum x

CROSSREFS

Cf. A248939, A248953, A000217, A014132.

Sequence in context: A221757 A189424 A009371 * A101502 A118440 A247119

Adjacent sequences:  A248949 A248950 A248951 * A248953 A248954 A248955

KEYWORD

sign

AUTHOR

Reinhard Zumkeller, Oct 18 2014

STATUS

approved

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Last modified February 20 15:00 EST 2018. Contains 299380 sequences. (Running on oeis4.)