This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A248939 Table read by rows: wrecker ball sequences starting with n. 9
 0, 1, 0, 2, 1, -1, -4, 0, 3, 2, 0, 4, 3, 1, -2, 2, -3, -9, -16, -8, -17, -7, -18, -6, 7, 21, 6, -10, -27, -45, -26, -46, -25, -47, -24, 0, 5, 4, 2, -1, 3, -2, -8, -15, -7, -16, -6, -17, -5, 8, 22, 7, -9, -26, -44, -25, -45, -24, -46, -23, 1, 26, 0, 6, 5, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS A228474(n) + 1 = length of row n. LINKS Reinhard Zumkeller, Rows n = 0..16 of triangle, flattened Gordon Hamilton, Wrecker Ball Sequences, Video, 2013 FORMULA T(n,0) = n; There are three cases for k > 0: case T(n,k-1) > 0:   if T(n,k-1) - k != T(n,m), for all m=0..k-1 then T(n,k) = T(n,k-1) - k, otherwise T(n,k) = T(n,k-1) + k, case T(n,k-1) < 0:   if T(n,k-1) + k != T(n,m), for all m=0..k-1 then T(n,k) = T(n,k-1) + k, otherwise T(n,k) = T(n,k-1) - k, case T(n,k-1) = 0:   T(n,k) = 0; row ends, i.e., k = A228474(n). EXAMPLE 0:  0; 1:  1  0; 2:  2  1  -1  -4  0; 3:  3  2  0; 4:  4  3  1  -2  2  -3  -9  -16  -8  -17  -7  -18  -6  7  21  6  -10  -27  -45  -26  -46  -25  -47  -24  0; 5:  5  4  2  -1  3  -2  -8  -15  -7  -16  -6  -17  -5  8  22  7  -9  -26  -44  -25  -45  -24  -46  -23  1  26  0; 6:  6  5  3  0; 7:  7  6  4  1  -3  2  -4  3  -5  -14  -24  -13  -1  12  -2  13 29 . . . . . . . . 1730  3445  1729  3446  1728  3447  1727  3448  1726  3449  1725  0; 8:  8  7  5  2  -2  3  -3  4  -4  -13  -23  -12  0; 9:  9  8  6  3  -1  4  -2  5  -3  -12  -22  -11  1  14  0. PROG (Haskell) import Data.IntSet (singleton, member, insert) a248939 n k = a248939_tabf !! n !! k a248939_tabf = map a248939_row [0..] a248939_row n = n : wBall 1 n (singleton n) where    wBall _ 0 _ = []    wBall k x s = y : wBall (k + 1) y (insert y s) where                      y = x + (if (x - j) `member` s then j else -j)                      j = k * signum x (PARI) row(n)={my(M=Map(), L=List(), k=0); while(n, k++; listput(L, n); mapput(M, n, 1); my(t=if(n>0, -k, +k)); n+=if(mapisdefined(M, n+t), -t, t)); listput(L, 0); Vec(L)} for(n=0, 6, print(row(n))) \\ Andrew Howroyd, Mar 01 2018 CROSSREFS Cf. A228474 (row lengths - 1), A248961 (row sums), A248973 (partial sums per row), A248952 (min per row), A248953 (max per row), A001532 (Recamán). Cf. A248940 (row 7), A248941 (row 17), A248942 (row 20). Sequence in context: A010247 A087605 A251636 * A106246 A136674 A144383 Adjacent sequences:  A248936 A248937 A248938 * A248940 A248941 A248942 KEYWORD sign,tabf AUTHOR Reinhard Zumkeller, Oct 17 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 17 18:48 EST 2018. Contains 317276 sequences. (Running on oeis4.)