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A101261
a(2n-1) = 1; a(2n) = a(n)th smallest positive integer not among the earlier terms of the sequence.
2
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.
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
KEYWORD
easy,nonn
AUTHOR
Leroy Quet, Dec 17 2004
EXTENSIONS
More terms from Robert G. Wilson v, Jan 13 2005
STATUS
approved