A101261 a(2n-1) = 1; a(2n) = a(n)th smallest positive integer not among the earlier terms of the sequence.

1, 2, 1, 4, 1, 3, 1, 8, 1, 5, 1, 9, 1, 6, 1, 16, 1, 7, 1, 14, 1, 10, 1, 21, 1, 11, 1, 19, 1, 12, 1, 32, 1, 13, 1, 24, 1, 15, 1, 34, 1, 17, 1, 30, 1, 18, 1, 45, 1, 20, 1, 36, 1, 22, 1, 47, 1, 23, 1, 40, 1, 25, 1, 64, 1, 26, 1, 44, 1, 27, 1, 59, 1, 28, 1, 51, 1, 29, 1, 74, 1, 31, 1, 56, 1, 33, 1

Offset

1,2

Comments

The sequence {a(2k)} forms a permutation of the integers >= 2.

Links

Table of n, a(n) for n=1..87.

Example

a(12) = the a(6)th (the 3rd) smallest positive integer not among the first 11 terms of the sequence. Not among the first 11 terms are 6, 7, 9, 10,... The 3rd of these is 9, which is a(12).

Mathematica

a[1] = 1; a[n_] := a[n] = If[ OddQ[n], 1, Complement[ Range[100], Union[ Table[ a[i], {i, n - 1}]]][[a[n/2]] ]]; Table[ a[n], {n, 90}] (* Robert G. Wilson v, Jan 13 2005 *)

Crossrefs

Sequence in context: A256578 A127461 A329900 * A214057 A067614 A341308

Adjacent sequences: A101258 A101259 A101260 * A101262 A101263 A101264

Keyword

easy,nonn

Author

Leroy Quet, Dec 17 2004

Extensions

More terms from Robert G. Wilson v, Jan 13 2005

Status

approved