A125566 a(1)=1. Take the positive integers, then reverse the order of the integers a(m+1) through a(m+a(n)), where m = 1 + Sum_{k=1..n-1} a(k).

1, 2, 4, 3, 8, 7, 6, 5, 11, 10, 9, 19, 18, 17, 16, 15, 14, 13, 12, 26, 25, 24, 23, 22, 21, 20, 32, 31, 30, 29, 28, 27, 37, 36, 35, 34, 33, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 67, 66, 65, 64, 63, 62, 61, 60, 59, 86, 85, 84, 83, 82

Offset: 1

Author

Leroy Quet, Jan 01 2007

Keywords

• easy
• nonn

Comments

This sequence is a self-inverse permutation of the positive integers.

Examples

			The sequence grouped by descending runs, where the n-th descending run, after the first 1, is made up of a(n) terms: 1, (2), (4, 3), (8, 7, 6, 5), (11, 10, 9), (19, 18, 17, 16, 15, 14, 13, 12), (26, 25, 24, 23, 22, 21, 20), (32, 31, 30, 29, 28, 27), (37, 36, 35, 34, 33), (48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38), ...
		

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..10056
• Rémy Sigrist, PARI program
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

Cf. A038722.

Programs

PARI

\\ See Links section.