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A273863
The successive numbers of integers visible between two even terms are given by the sequence itself.
0
0, 2, 1, 3, 4, 5, 6, 7, 9, 11, 8, 13, 15, 17, 19, 10, 21, 23, 25, 27, 29, 12, 31, 33, 35, 37, 39, 41, 14, 43, 45, 47, 49, 51, 53, 55, 16, 57, 59, 61, 63, 65, 67, 69, 71, 73, 18, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 20, 97, 99, 101, 103, 105, 107, 109, 111, 22, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 24, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 165, 167, 26
OFFSET
1,2
COMMENTS
The sequence starts with a(1)=0. It is then extended with the smallest integer not yet present and not leading to a contradiction. The sequence is a permutation of the integers >=0.
EXAMPLE
The first two even terms that appear in the sequence are 0 and 2; between 0 and 2 there are 0 integers and this 0 corresponds to the starting 0 of the sequence.
The next even term is 4 and between 2 and 4 there are 2 integers [which are 1 and 3] and this 2 corresponds to the next term of the sequence.
The next even term is 6 and between 4 and 6 there is 1 integer [which is 5] and this 1 corresponds to the next term of the sequence.
The next even term is 8 and between 6 and 8 there are 3 integers [which are 7, 9 and 11] and this 3 corresponds to the next term of the sequence.
The next even term is 10 and between 8 and 10 there are 4 integers [which are 13, 15, 17 and 19] and this 4 corresponds to the next term of the sequence.
Etc.
CROSSREFS
Sequence in context: A288118 A155963 A375326 * A273864 A058684 A226054
KEYWORD
nonn,base
AUTHOR
Eric Angelini, Jun 01 2016
STATUS
approved