A118833 - OEIS

A118833

a(1) = 1. a(n) = (|a(n-1) - n| + 1)th positive integer which does not occur earlier in the sequence.

1, 3, 2, 6, 5, 7, 4, 12, 11, 9, 13, 10, 16, 15, 8, 24, 23, 21, 18, 19, 20, 22, 17, 31, 30, 28, 25, 29, 14, 46, 45, 43, 40, 36, 27, 42, 37, 32, 44, 38, 35, 49, 48, 41, 47, 33, 61, 60, 58, 55, 51, 34, 72, 71, 69, 66, 62, 53, 57, 52, 67, 59, 56, 70, 64, 50, 84, 83, 81, 78, 74, 54

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

This sequence is likely a permutation of the integers.

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10000

EXAMPLE

The first 8 terms of the sequence are 1,3,2,6,5,7,4,12. |a(8) - 9| + 1 = 4, so a(9) = the 4th positive integer which doesn't occur earlier in the sequence (i.e., the 4th integer in the sequence 8, 9, 10, 11, 13, 14, ...). Therefore a(9) = 11.

MATHEMATICA

Fold[Append[#1, Complement[Range[Max[#1] + (d = Abs[#1[[-1]] - #2] + 1)], #1][[d]]] &, {1}, Range[2, 72]] (* Ivan Neretin, Mar 13 2017 *)

CROSSREFS

Cf. A118834.

Sequence in context: A244987 A171417 A347740 * A268823 A046877 A067587

Adjacent sequences: A118830 A118831 A118832 * A118834 A118835 A118836

KEYWORD

easy,look,nonn

AUTHOR

Leroy Quet, May 01 2006

EXTENSIONS

More terms from Franklin T. Adams-Watters, Nov 28 2006

STATUS

approved